You can't force people to be truthful online, just like you can't fill up every crack on the Earth with cement.
If I ask you to confirm you haven't changed your number and you outright lie then I'm sorry but it is what it is.
It is completely disingenuous to frame this as though Bob walked up to Alice after lunch and asked her "Has the phone number you used for authentication changed?" and she lied and said "No".
And it seems obvious that in most cases, users that lose access to 2FA methods are not asked "has your 2FA changed?" while they still have access to the account. It is far more likely that one day their cookies are reset or google decides it's time to reauthenticate and they realize that they changed their phone number when they switched phone plans a week ago, and they hadn't thought about the consequences.