So, I wouldn’t assume it’s great for end users without digging into the details. Don’t forget the last time they did privacy regulations they created an unending wave of click yes to accept cookies.
PS: Looking at rapid downvotes I see people disagree, but mandatory interoperability would presumably force them to accept SpamNetwork101, SpamNetwork102 … etc.
WhatsApp replaced SMS as a free alternative with media. Sms is just a protocol. It is not necessary that a replacement is walled garden, especially not under the sole guise of spam protection - something that is being done very poorly anyway.
Depending in the specifics everything from Yahoo! Messenger to MMO chat either needs to get shut down or made interoperable.
And even if you for some reason don't want to restrict your requests, you'll probably still be fine - Gmail handles protects me from spam pretty well.
Is say MMO chat a social network?
Using this model it would better to have multiple lists though, or at least tagging within the general contacts list, so tag-based lists could be allowed by certain apps (to keep business and personal messaging separate for example).
New person goes to chat requests, they communicate through another channel they've sent you a message, you go open the graveyard of chat requests and accept theirs.