As said above, there is zero reason for Bob to stay this size, given he will be 58 in December.
But it's quite possible that he's just on a few hundred MG's of testosterone weekly. He has already earned the muscle [Bob competed from 1981 to 2006], and he's not in contest shape anymore.
Bob is also mesormorphic.
It would be suspicious to me if he maintained that size and suddenly looked way leaner. I'd say it's possible that Bob is just on a hefty dose of TRT.
Muscle memory is a real thing.
Like The_Coach said, training is in your DNA when you've done it for four decades. And both Bob and Coach have been training for over four decades.
If Bob suddenly shows up on a YouTube video at the same body weight, but with his body fat considerably down, I would assume he is getting brave in his doses.
Until then, I would assume he is doing a generous dose of TRT. Not necessarily more than that.