or when rumble announces bitcoin tipping for their users but it's custodial, or when miners mine bitcoin but it's custodial. the argument is just to make a point but not to convey any meaningful information.

just custodial bitcoin

Scaling Bitcoin requires self custody IMO, that's a useful technical definition. Similarly, using cashu means using Bitcoin, same as using wallet of satoshi is using Bitcoin, or cashapp. Using a bank account is using Fiat. The bank account isn't fiat either. Same with credit cards. I'm ok if anyone disagreed with that though, since the disagreement has no practical implication. For me this is all sophistry. I don't like arguing about meanings of words with no productive outcome. Let the philosophers do it. As long as we agree on the technical properties of these things, we can find agreement on a deeper level IMO.