Probably not all that relevant, however native drivers apparently enforce it. There are games out there that make use of D3DCREATE_PUREDEVICE, so it doesn't hurt to make sure we don't end up in weird situations.
To be fair, I fail to see how this flag would ever have made any sense outside of HWVP (and maaaaaybe mixed VP), but there's nothing explicitly mentioned in the spec as far as limitations go, so this was based purely on observed behavior.
Probably not all that relevant, however native drivers apparently enforce it. There are games out there that make use of D3DCREATE_PUREDEVICE, so it doesn't hurt to make sure we don't end up in weird situations.
To be fair, I fail to see how this flag would ever have made any sense outside of HWVP (and maaaaaybe mixed VP), but there's nothing explicitly mentioned in the spec as far as limitations go, so this was based purely on observed behavior.