+1 to this.
I am trying to present a "drawer" (read: sheet with presentationDetents()) on top of another View. Both the parent and the drawer should be interactive simultaneously. Currently, it appears that any time a sheet is displayed, it s forced to be modal, as @aaronjedwards noted.
This means my really-crummy implementation of a drawer will have to live on, much to my dismay, even though the new presentationDetents() API seems made for my use-case.
I filed FB10636765 on this issue.