He'll have to cut his studs anyway, it would make way more sense to put the subfloor in first.
What were you planning for a subfloor Stang? I just did a suite for a friend and for a subfloor they used 3/4 osb over that waffle membrane. If your floor is pretty flat it is way cheaper than the dri-core. You can do a whole basement in a few hours this way. If you frame first every wall breaks your drainage paths.
