This feature by Karman Games is called "auto-complete". It is also utilized in other games they make, such as Euchre.
Basically, if there is only one mathematical outcome, then there is no point in playing the rest of the hand out (or at least, that's how Karman Games sees it).
Although it doesn't (and can't) occur to the same extent, you can technically apply this feature on tabletop as well:
If you know you have the top X cards in Hearts (or Euchre), then some people will flop their entire hand down, rather than playing each card individually.
Note that you may not even have the top X cards in Hearts/Euchre to do this... if you do the math correctly and/or remember what cards have already been played, you can figure out the number of hands/tricks you are guaranteed to win (so long as you play them in the correct order).
If your calculation ends up being incorrect, and you flop down your hand mistakenly, it is called a "renege" and you will be penalized for it.