In case you haven't resolved this yet, the only way I know of removing flickering when quickly removing/adding overlays is to first add the overlays, then remove the overlays. Even in satellite view, this will remove the flickering. Though this creates another problem; it leaves artifacts of old overlays - in particular when zooming in/out.

@Claude31, @endecotp thanks for your perspectives. No I am not expecting Apple to fix my issues or help me through a bandaid when I am submitting bugs. My problem is mostly that, being a small startup developer, I have no time to create elaborate reports in particularly when being asked to write test code by Apple. Apple is not giving feedback of any kind and can obviously not know how much time and effort I can give to a particular issue. As you said, it is not a bidirectional channel - this makes it very clear for me; I am not in a position to provide bug reports and will stop doing this. Much better to spend time hunting for solutions.

Oh hey, hmm. Not quite sure I follow you're testing method but I did notice that after I do a fold, that file must be saved. if the file has no changes (only a fold), it isn't actually saved, making a simple change (add a space somewhere) and saving seems to work; reopening the project now has the methods still folded. I see now what trips me up; since I have a few tabs open with a collection of files, some tabs have the same file open but apparently operate on a different view. I.e., folding methods in one does not fold them equally in the other. That is not necessarily bad (I can understand why you want to have different views of the same file) but leads to confusion whereas it pertains to a method's/section folded state.