This has been there from the beginning, has been raised with developers multiple time and has been dismissed as 'by design', like DM1 says. Why anyone would think that two render passes in an app that focuses so heavily on painting strokes, be it for drawing or masking, is a good idea to boost performance is beyond me. I have long stopped using Photo for drawing and painting, it's not possible to seriously work this way. Occasionally, I do some file print prep but even that I can now do elsewhere. For digital painting, I recommend Procreate (fantastic painting experience) and Clip Studio Paint (sophisticated image editing), both solid, reliable apps with superb painting capabilities.