At least your use case would be served well by enabling LAN mode, which doesn't let the printer talk to the internet, even if you want it to (and I want mine to).
The problem is trust. I don't want to get into an adversarial relationship with my printer over networking.
I could enable LAN mode and trust the mode does what it says.
I could trust others firmware reverse engineering to verify LAN mode does what it says.
I could isolate it on it's own wifi and I could block it at the home firewall from accessing the internet, to be sure.
But it was easier to simply leave it off my network.
The problem is trust. I don't want to get into an adversarial relationship with my printer over networking.
I could enable LAN mode and trust the mode does what it says.
I could trust others firmware reverse engineering to verify LAN mode does what it says.
I could isolate it on it's own wifi and I could block it at the home firewall from accessing the internet, to be sure.
But it was easier to simply leave it off my network.