I'm not sure I am understanding you correctly but:
If you pre-purchased the game here on itch during the early access dev builds phases, you should have been given an option to redeem the game on Steam. That option should still be available to all early access buyers. New purchases will not receive Steam keys
And in case you mean the other way around, if you purchased the game on Steam you do not automatically get access to the DRM free version here. You will have to purchase the game again here in order to access the DRM free itch builds. The game isn't any different here or there though, so if you already have access to the game on Steam you are not missing out on any features present in this version.
Does that answer your question?