Requires even more work and even more budget.

It really doesn’t. They include both anyway, there’s no reason they can’t do it as a separate download. Rainbow 6 Siege did it back in 2015 with their ultra high definition textures pack which is a 30gb download for a game that’s 60gb without it. Lots of players have no use for the ridiculously high-definition textures, it would definitely make sense to separate them from the main package and cut possibly several hours or even days of download time for some people.