I am an engineer working for a registrar and we've been told by at least one TLD that there is no difference. We used to "mask" the registrant email regardless

I am an engineer working for a registrar and we've been told by at least one TLD that there is no difference. We used to "mask" the registrant email regardless of whether or not the customer had opted-in for proxy registration, and we were told this was not allowed by the TLD operator.