Are you able to share these reports? Any information about what browser they are on? Any browser extensions? I just tested on latest Chrome & Firefox with no extensions and the confirmation dialog appeared as expected.
I apparently just removed my teams' game submission from mobile without noticing while scrolling on my screen. It was like a few mins becore the end of the game jam so well... it was too late before we noticed. We had a lot of good comments so we are a little sad to have lost them...
I didn't get any dialog box to confirm. I was on Firefox on mobile (Firefox Nighly to be precise but not sure it matters).