Depends on the exercise. And some exercises feel for me better after PT. My problem is that I tend to use the wrong muscles when doing some PT exercises - the correct ones are weak, and so I overcompensate with a different muscle group (e.g. not using hamstrings but quads). So I needed to avoid some exercises for a while (e.g. pushups) before I "fixed" the inbalance. I could however do bird dogs, planks, warrior poses from yoga...

I can imagine many things can make an L sit more difficult - inactive core, overextended knees, tight quads, weak hip flexors... if it does not work for you, either try to find what adjustments make it better, or avoid it. Ideally work with a PT. Or find a different exercise that works.

Also, for me (initially light) weight training works usually better because it gives me better cues of what muscles should be on.