I am not sure it’s cause any problem. 
I reported it because of the functionality of non dismissable modal. But it’s probably the same as when you click the Cancel button. It may got some problem if the modal’s goal is block or forces the user to choose from options and the footer buttons not contains Cancel button. I don’t think there are any modal in core which affected with this. But it can affect custom modals, like the Guest Gate Theme Component has a setting to makes the modal dismissable=false and the setting main goal is block the content what now can be easily bypass with swipe down.
But maybe it can be easily fix with touch-action: none? I didn’t check it yet…