They might have used them for fine-tuning, but there is no way that they produced enough samples to train a model from zero.

That's kinda a different case than what everyone is referring to when they're talking about this

However, it's an interesting point: do we know those voice actors are being paid the same as if they did the lines all themselves or is this a studio cheaping out on paying actors to do the job?

There might have been a load of actors who turned the job down before they found someone desperate enough for the money or naive enough to not realise it will likely drive down wages for voice actors if this becomes commonplace.