You’re gonna get a wide variety of the school of thought on this topic. So take my point of view with a grain of salt. My point of view comes from over a decade of specific amateur power lifting, over 25 years of consistent weight training, and with marrying up amateur XC racing for a decade now with weight training.
Technically, TSS only applies to cycling. However, I know some runners who track TSS. You can technically track it on gym work with what Training Peaks calls HRTSS to assign a stress value to your workout. Friel also has a calculation for total weight moved by tonnage to come to a tss calc.
Personally, I assign a TSS score to my workouts when they are heavy as there is legitimate fatigue being built up. Right now I’m only lifting/weight/body training about 7 hours across 3 days a week. That’s about to go up to 12-14 hours and 6 days a week in addition to still riding 9-14 hours a week - albeit at lower intensities. You betcha I’ll be gaining fatigue by working out. If I left my charts alone, and didn’t model the workout stress, my charts would say I would be sky high on form and that’s simply not right.
I’ve used both methods (hrTSS and Friels calculations) they both come out to be pretty much the same between 40-50 hrTSS for what I’m doing. Your results may vary. Now, that said, I’m not lollygagging around. I only take about 30-45 seconds break between sets and I’m doing 3x20 on main moves right now - up to 12 main moves a session when I’m hitting legs, chest, back all at once as I am right now.
It takes a while, but I can call my form and fatigue on a given day now without having even looked at Training Peaks for a week and be within 1-2 points. I can also call my daily FTP by how I feel. The more you get in tune with your body, the more you can zero in what real fatigue is doing and what it feels like and assign a number to it.
Regarding yoga, I personally wouldn’t assign a score to it, mainly because I fall asleep on the floor on some of those.