In terms of end-to-end encryption I don’t mind if they have my phone number or not, if it’s done right.
Let’s use signal for example, because honestly they do it pretty decently, the most information that you can obtain from signal in a data information request is the date and time that an account is created, and the last time the account went online.
Actual content such as the user’s contact list, the people that user was talking with(including groups), and of course the messages that you sent are fully end to end encrypted meaning that signal does not have access to it meaning that they cannot give that information out in a data information request as they never had it in the first place.
The most that signal is able to confirm in a data information request, is yes this specific account ID has a signal account and this is the last time they went online.
and what is that going to give them? The information that they have is yes, they have an account, and that’s also saying that they used an actual number and not a VOIP number for registration. but if they are asking via phone number, they will already have that information at hand. They won’t get any information about what chats that number is part of, or even any info really at all, anything about the account is encrypted and not visible.
If they are able to provide my phone number without knowing the info you said there, there is some other leak already involved, and either way they won’t get anything but a “yes he has an account and he was last connected on X”