IMO I don’t think this is what open core is. Open Core should mean that, if a user is not happy with a commercial offering, they are able to roll their own. Perhaps it would take them a bit of time operationally to do this. Maybe they need to spin up their own infra (eg cloud VMs, cloud database etc) but this should be possible for them to do this within a reasonable amount of time.
I think the change being rejected here is fundamental to the operation of this tool. Without SAML auth, you simply cannot deploy it yourself for your internal users.
I am willing and open to other views on this. But I am not convinced that project owners should be allowed to call their project open core without having some reasonable burden to allow the software to be self hosted.