BUT they could've easily made it simply audio only or even put it as free DLC pack for those wanting it.
People did want japanese voice acting, they didn't want 20 GB of extra space taken.
If it's DLC, it wouldn't be free.
Capcom and SE do the sleazy "foreign dub as paid DLC" all the time in Japan even if the Western build has dual dub built in. People complained about the one time JP audio being DLC in a Western release (free first month, 15$ later) for FF XIII-3 and that one bombed, hence why SE is putting the extra effort here.
Incidentally, this particular PC port here doesn't have dual dub in Asian regions.
I agree about the size though, something went wrong or they just didn't compress the audio/videos. At this point I find it expected that SE wouldn't go through the effort of fixing the various graphical effects that would be broken by resolutions higher than 720. It's a lazy, minimum effort port. Better to keep expectations in check (and that also applies especially for the iOS DQ ports, who are all in some capacity (save for the first two games) inferior to the original)