It really depends on how many leaves we’re talking; a thin, evenly distributed layer? Yeah that’s just mulch and is great. A thicker layer that turns slimy and dense? That grass is a goner. Area and species of leaves probably pays a big part I imagine. I have an area near a fence where the leaves piled up and were left a year and now there’s no grass there, even a couple years later (there’s a super embedded layer of decomposing leaves that’s blocking everything else out even after removing the bulk of the leaves)

Of course, there’s never room for nuance in these conversations.