When you use the hide_title_bar=True attribute with present, you close the app with the 2-finger-swipe-down gesture. If your use case requires it, Gestures supports disabling this gesture with:

Gestures.disable_swipe_to_close(view)

where the view is the one you present.

You can also replace the close gesture with another, by providing the "magic" Gestures.close_app method as the gesture handler. For example, if you feel that tapping with two thumbs is more convenient in two-handed phone use:

Gestures().add_tap(view, Gestures.close_app, number_of_touches_required=2)