Being flexible is important, but the latest research shows that heavy lifting improves flexibility about as much as a dedicated stretching program: https://pmc.ncbi.nlm.nih.gov/articles/PMC9935664/
Yeah, I noticed that after a certain age if you want to retain ability to do the movement you need to do that movement. Doing 20 others won't help with that one.
On the phone so can't see study details - what do day consider strength training ? I used to lift heavy (well by regular people standards) and for example my squat mobility was shit. Trying to improve that with significant load would have ripped my tendons I feel. Decreasing the load to the point where it wouldn't might as well be called stretching cause it wouldn't qualify as heavy lifting. Also most powerlifters I know have shit mobility.
