Also, when they’re recording the audio, they’re usually not just reading through the whole script in one go
They’re probably doing multiple takes of most of the lines, changing little things until they get the take that feels right
So you’d end up with a bunch of choppy little cuts instead of a nice long continuous shot of the VA doing their thing in a recording booth like OP is probably imagining
They record the audio, then match the animation to the voices.
They don’t watch the animation and try to match the voices, that only happens for a dub.
That’s true of western animation, but Japanese anime is drawn first, then the VAs match their performance to the footage.
Also, when they’re recording the audio, they’re usually not just reading through the whole script in one go
They’re probably doing multiple takes of most of the lines, changing little things until they get the take that feels right
So you’d end up with a bunch of choppy little cuts instead of a nice long continuous shot of the VA doing their thing in a recording booth like OP is probably imagining