I had started to notice the same thing, though I don't know if it is new or not. You can even see it occur on the angular material site, so it isn't an implementation issue. Open that first dialog without animation button a few times. If you click outside to close, the overlay is leaked, not the dialog component it self, but if you click anywhere inside the dialog at all, that becomes a leak.

https://material.angular.dev/components/dialog/examples