Pokemon Go has never revealed too much about some of the in-game mechanics. Whether it was Pokemon IVs, spawn locations/times, egg hatching, etc. — the Pokemon Go has almost prided itself on leaving it up to players to figure exactly how most of the game actually works. This applies to some of the shortcuts found in the game, things like swiping left/up/right from the Poke Ball icon to quickly access your Pokemon Bag, Shop, or Items.
In fact, users are still discovering new tricks. The latest of which involves quickly switching out your Pokemon while engaged in a gym battle. Simply swipe up to quickly swap out your Pokemon for the next one on deck, something that’s much quicker than reaching over and tapping the onscreen button in time. When milliseconds spell death for a Pokemon, it’s gestures like these that are the difference between winning, or using even more revives. With your Pokemon now fainting even when leveling up your own gyms, this should come in handy to keep those revives nice and stocked up.
Although it sounds like this gesture may have only been added in a recent update, it’s entirely possible it was there from the start we all just missed it. In either case, it’s little discoveries like this that have largely contributed to the game’s success (we saw a similar trend with Snapchat). People digging around, posting on forums their discoveries, it gets people talking — and that’s a good thing.
[Reddit]