I feel like the main reason, though, was that they could easily afford real voice actors.

that's... exactly what they did. They hired real VAs that recorded some lines that are used as-is in the game, and stuff for training, which is to make more dynamic commentary about the match. It was a controversy because people saw "AI" and lost their marbles. Nothing wrong if it's contracted/licensed training data.

Ability to do it realtime in video games in general seems huge.

There's a bit thing atm around human creative work being replaced by AI; even if a voice isn't cloned but just generated by AI it gets people frothing as if human hands in factories haven't been replaced by robots, or a human rider on horseback wasn't replaced by an engine.