Your other option would be to switch it to a white list ie making it block all unknown/private numbers but I don't see that as ideal you might block important texts or verification texts from banks etc
Actually, in this case, the phone would internalize all blocked numbers so that they could not be seen. This addresses a specific issue and may not work for all users, but it could be a highly useful option.
This is for a specif requirement to remove all traces of numbers that are being used to harass and take advantage of an individual who is not able to defend themselves. There is no other what if here. We need it to be totally removed. Period.
There will always be a list, but if your use case is that you simply don't want to see the numbers you can press the 3 dot menu in recent tab and choose hide blocked calls but a black list will always store the numbers you want block on the phone.