Dragon Ball Fighterz and Super Smash Bros. are very different games though.
With Goku, Vegeta, Goku, Vegeta, Goku, Vegeta, Vegito, Gogeta, Goku, and Goku, Dragon Ball Fighterz clearly gives no cares about two characters being in the same place.
Super Smash Bros. on the other hand, tends to try and make sure that this doesn't happen beyond multiple players picking the same character, like how King Dedede is removed from Dream Land. Granted, it's not completely consistent (Duck Hunt isn't removed from Duck Hunt when Duck Hunt is present...I hate how that makes perfect sense in context) , but there is at least a precedent for this attention to detail. It's not to say that they can't ignore something like this, but it's also not to say it's completely ridiculous to think it would need to be addressed.