Been awhile since I played actual minesweeper, but shouldn't revealing a tile with a number on it which otherwise has empty neighbors also uncover those neighbors? I could swear that's how the original works.
I've tested on an iphone mini, and even though the dialog is quite big on it, so I should indeed try and shrink it, it doesn't prevent completing the tutorial. But it looks like I wrongly assumed this would be the smallest phone I could test it on.
And as far as I know, the empty tiles only gets uncovered if you uncover another empty one, so I followed this principle. If that was also the case when you uncover a number, this would reveal too much.
iPhone SE, Safari
And if you're able to send a screenshot, that'll be super useful. As at the moment, when testing in chrome dev tools, with iphone SE selected, it looks like it doesn't display the right size of the phone (or maybe I've misconfigured the dev tools), as the dialog box doesn't prevent from completing the tutorial.