Not necessarily.
At my school, the houses were owned by a local “House Corporation” that was a separate legal entity from the National and run by local alumni. The land was owned by the University and leased to the house corporations under a separate agreement, which obligated the University to buy the house at fair market value should it decide to cease leasing the land.
I’m guessing that there’s a similar situation here, with the house and land being leased. While the SAE National has revoked the charter and severed ties, the chapter’s house corporation might be the actual leasee, and therefore able to take it’s own legal action independent of the other parties.
According to the SAE Website the building was the property of the university. The wanted to make it clear that it was the university who was evicting the students and not the fraternity. Of course since they revoked the OU chapter's charter then the former frat boys had no reason to be living there so the University could tell them to leave.