Only my single has a PM. I wear a HRM for all my workouts: single, tandem, strength, hikes, walks, runs, etc. I upload every workout to TrainingPeaks: For my single bike workouts, I can click back and forth on TP between TSS and hrTSS. On steady-state roller rides, those two numbers are usually about the same, which to me indicates that I have my zones about right. On interval workouts of course TSS will be larger than hrTSS.
Getting down to subject of this thread, we see that hrTSS from strength workouts will always underestimate real TS. Nonetheless, I do record it and it becomes part of my CTL. I don't let the fact that it might be too low bother me. As I get closer to my major cycling events I greatly decrease or stop doing strength work anyway. Since I've been doing this for quite a few years, I know about what I need in terms of CTL to ride as well as I can expect in various events.
Basically, I ignore the fact that my CTL, Form, and Fatigue might not perfectly represent my physical condition at the end of every week and go somewhat by feel. That said, my experience is that my numbers are usually closer to reality than my emotions or inner assessment. I've had weeks where my legs were sore all week and I've felt strong on the Sunday ride anyway. Though usually If I get too far in the hole w/r to Fatigue, I take a day off. For me, increasing CTL by about 3/week works well but hey, I'm old and not a talented athlete anyway. One needs to get experience with what works and a good way to do that is to upload all your workouts somewhere. IME of course.
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Results matter