In the anime, the basic Poké Ball is the most commonly used of all
varieties, with other varieties appearing either very few times or not
at all. A vast majority of Pokémon are shown to be stored in regular
Poké Balls, to the point that large collections of Poké Balls can be
seen with no variation among them.
So it is just the anime.All sorts of things can happen.Maybe for checking they open the pokeball and check what pokemn is there and the Pokemon return baack to the pokeball.It is just the anime like I told you.