Yeah the muscle and bone development you get from lifting that heavy really help out in your old age. It's kind of like a reservoir of ability.

I did a lot of grinding out heavy reps when I was younger and less experienced(mid-30s now) but now I am suspicious of that whole idea. If I stick to two reps before failure - i.e. when I start really slowing down the movement - my recovery time post-workout becomes much better and I don't experience as much collapse-into-bed tiredness, but I'm still seeing progression. There's an old broscience debate about whether muscle damage is critical but my own observation is that if it is, you don't need a lot of it, and doing so would favor PED users with tons of recovery capacity.

I also shifted my focus away from the largest muscle groups towards hip/core/shoulders, under a similar reasoning that if what I'm up against is mostly recovery capacity, the small muscles can be trained safely at higher frequency and will have the most impact on injury prevention and avoiding the stoop, rounded shoulders, etc. that afflicts the old.