To be fair it's pretty dumb given Steam's current market position to not release on Steam. Given that is unlikely to change the "strings" on this deal really don't seem that bad. There is nothing stopping you from also publishing on Oculus store (if they allow non-exclusives) in addition to SteamVR.

The only thing that would make it nasty is if there is nasty clauses in the case you are unable to meet the prepaid Steam revenue. However I don't know the answer to that.