He's not natural, but much of what he says rings true. And, no, there is no accounting for the glasses.
The joint problems he brought up are probably the biggest issues for older people. Once a joint is shot, it's really hard to do much of anything physical with it, especially cardio work and weight training.
My shoulders would agree with you, particularly my left one. Fortunately, I can work around it and still do compounds, although doing laterals is just asking for trouble. I've always hated them anyway. Also, apart from cumulative injuries acquired over the years, I think it's easier to get hurt as you get older, so proper form becomes that much more important. But the points about BMR, diet, and maintaining leanness are on point. I've given up trying to regain some of the size I had even as late as in my 50s. No finessing of my routine is going to get that back. I tried, even though I knew it was pretty much a pipedream. So, maintaining what I have as long as I can while staying as lean as I possibly can is about all I can do. And I do have to be more attentive to my caloric intake than I did years ago. On the plus side, my bodyweight scale tells me my bodyfat is about 2 percentage points lower than it was 5 years ago while my weight is essentially unchanged. I take some comfort in that even though I know the scale itself is of questionable value apart from telling me my weight.
So now that I'm going on 53, I've gotta ask you: At what age did you first notice your size diminishing past the point of realistically getting it back? I figure I might as well know what's coming down the pipeline than be surprised when it happens.
I think it began somewhere in my mid-50s, although I had been very slowly losing size for some time before then. But I would say that it was not especially noticeable yet, even though I was already a few pounds lighter. However, keep in mind that I began streamlining my routine a few months before my 54th birthday because I simply could no longer handle the volume I had been doing at the full level of intensity that I always felt the need to do. So did my size diminish because I minimized my routine? Or was the writing already on the wall because I could no longer handle the volume? Sounds moot, right? Also, please keep in mind that in 2013, just before my 55th birthday, I had a mishap outside the gym that severed two tendons in my left shoulder. (My right shoulder was previously my "problem" shoulder because I had severed one tendon in it several years before that and probably in the gym. Now, my right shoulder is the "good" shoulder.) So that may have played a role, per the video above. However, apart from some isolated shoulder exercises which give me grief, and which I hadn't done in years anyway, I still "seemed" to have maintained my strength for, say, pullups and dips, both of which I continued to do with a fair amount of added weight for my size until some years later when I opted for higher, slower, and more deliberate reps without the added weight. Even so, I am now about 20 pounds lighter than my best weight in my 30s when I was leaner than I am now. And remember, I'm not a big guy, so it has been quite a change. I still maintain the weight I had when I posted a few pics in 2019 in another thread in this forum although, as I noted, my scale tells me my bodyfat is a couple of percentage points lower now. I feel the need to keep saying that, even though the scale is of questionable value. In any event, you may find that you'll coast for a good while longer before going into a noticeable descent, especially if you have not suffered any injuries of note. So I wouldn't let it bother me if I were you. Although I was preoccupied in the past with wanting to add size, it is no longer my principal concern (perhaps out of necessity since it ain't happening anyway). Of course I want to hang on to what I have, such as it is, for as long as I can, but maintaining leanness is the thing for me right now. If I could add on a few more pounds of muscle, of course I would, but not at the expense of taking supplements of any kind. Not even creatine. But I'm quite short and so I don't think bulk looks especially good on a small man. I want to be that lean, chiseled guy (still working on it) who all the beautiful women out there don't yet know they're in love with.
After working out for over 35 years, I got to the age where close members of my family started dying. It made me lose my desire to continue. Then my son bought me a total gym, because he didn't want me to lift heavy weights over my head anymore. A game changer at the age of 63 with the only desire is to maintain fitness and not build muscle, but maintain it.
Safety first, of course. But I think most(?) people can still work up to going all out if they're doing the right exercises, the right way and on the right equipment, if any. I've read of people much older than us who are strength training to full intensity. With their doctor's okay, naturally. That's what slows down age-related sarcopenia, since the fast twitch fibers are the first to go.
I kept my size up to age 60 when I consciously decided to get (much) leaner. Figured it would benefit my joints and overall health going forward. Lost 35 # in 3 months and have kept it off +/- 5#. The lost size was offset by significantly more definition which actually looks better at age 64