That's true, usually with domain fronting you provide the (wrong) SNI. But the same strategy is happening here, you were supposed to provide SNI and you didn't to avoid some potential censorship but it's a headache for the provider

They won't have received a certificate for the IP as a name, it's relatively unusual to have those, the main users are things like DoH and DoT servers since their clients may not know the name of the server... historically if you connect to a TLS server without SNI it just picks a name and presents a certificate for that name - if there's a single name for the machine that definitely works, and if not well - domain fronting.

TLS 1.3 even specifies that you must always do SNI and shouldn't expect such tricks to work, because it's such a headache.