I was wondering about this, too. Wasn't keeping me up nights or anything, but one of those "hmmm" kind of thoughts. I keep thinking of strength training in the realm of what is going to benefit me the most as I age. What muscles are more important to help prevent injury? For me, those are absolutely core muscles, glute and hip muscles, and those little muscle groups that assist with balance more than the ones that help me do a heavy bicep curl.
This is why I was actually pretty enamored with STS 2.0 in the sense at least of the mobility and active recovery workouts. I also like to know that I can go down to--and get up off--the floor easily and anything that has me doing those kinds of movements is great news. I found the core workouts in STS 2.0 kind of lacking, to be honest. Her earlier workouts hit my core far better.
That said, I also loved all the heavy hypertrophy-focused work in STS 2.0. Aside from the visual gains, I did have capability gains, too - I could lift and squat heavier, and though there wasn't much cardio, the full body and lower body workouts, because of their heavy nature, still managed to elevate my heart rate and I didn't see much loss there as far as cardio-demanding activities (like hiking).
I've still unfortunately been having to avoid any heavy weight work for a while due to my tennis elbow. Unfortunately it doesn't just interfere with bicep curls, but also just holding heavy weights, period. So frustrating. I dare say it's been feeling a bit better lately, but I'm pretty sure if I tried something heavy right now, I'd probably reinjure it. So have to stay pretty light and conservative, still, with means no STS 2.0 for me, at least not with heavy weights.