The OP isn't complaining that their phone is roaming to a managed Wi-Fi _in preference to cellular_

They're complaining that it's not using their own Wi-Fi and causing real issues for their family members.

Trying to justify this behavior because "well, the ToS maybe said something about this" rightly deserves to get downvoted, as do your other points.

None of what you call out changes the fact that:

1. The OP is experiencing real issues, preventing them from using their own Wi-Fi at home

2. This is because of a configuration setting they cannot change on a device they own.

What SIM they're using, what ToS they've signed, none of that should matter when OPs goal is just "I want to be able to use my own Wi-Fi at home".