Its not about interoperability but rather the adopting of an open standard that any app can subsequently have access to, like how email works. We have this in RCS, it just needs Apple to openly admit iMessage is a terrible failure and adopt it as their messaging standard.
If anything Apple's adoption of RCS and the subsequent 100% interoperability of it with Android's default messaging app would likely kill off every 3rd party messaging app.
Except, if I understand the discussion and reporting correctly, the regulations in question don't require any single open standard, it requires messaging companies to provide some sort of messaging API to any other messaging company that requests it. There's not even a requirement for a given company to provide the
same API to every other company that requests one, so a given company could very well decide to tailor versions of the API to each requestor. The regulation lays the groundwork for the adoption of a bunch of different point-to-point gateways, not some universal standard. This would mean each connection from company A to company B would support the least common denominator of the features that are common between the two (and the least common denominator of all of the limitations on each feature). It doesn't take long before the least common denominator of feature sets that are uniform across all the platforms approaches... SMS. A universal standard we already have in place.
I lived through the beginnings of the internet (and the time before that, with email and Usenet over UUCP), and all the different addressing schemes one had to use to get from any given system to another system. Not really interested in going back to that mess.
Email addressing, exchange, and forwarding only works as it does today because of a whole host of standards that were worked out, debated, and agreed upon by a whole host of companies, researchers/universities, and other interested parties.
They didn't do it because of some government mandate or on some government timetable, they did it because they saw that it was mutually beneficial to everyone involved. This led, in particular, to RFC 821 "Simple Mail Transfer Protocol" and RFC 822 "Standard for the format of ARPA internet text messages" (the latter uses older naming for what we'd call email, and both have been subsequently superseded by newer revisions). And, notably, they devised a single standard that anyone could adopt and use to interoperate with the rest of the (expanding) group, they didn't build a collection of dozens of different ad-hoc "standards" connecting each pair of companies to each other (that's what they were getting
away from), which is what this upcoming regulation is requiring (that is, the regulation isn't
requiring separate/unique APIs for each pairing, but it isn't laying out one single standard, it's only mandating that any given company can require any other company to provide an API of some sort or another).
This is what you get when bureaucrats who do not possess the proper depth of technical knowledge, start writing laws dictating particular technology as if they did have that understanding. You get crap regulations. They either insist on fantastical technologically unsound things, or they have someone whispering in their ear telling them things to write that just happen to greatly benefit those who are whispering.
Assuming that the regulation in question is going to cause Apple to adopt RCS seems like a vast overreach in your assumptions. Your "100% interoperability" is never going to happen - there will
always be things each system can do that the other can't... unless you expect Apple to
entirely drop their own system and 100% switch over to RCS. I expect that will
never happen - if it did, iOS users would be pretty damn unhappy (because of all the niceties they'd lose - doesn't matter if RCS has
other nice things to offer or not). And RCS is, objectively, a bad standard - designed to drive control and profits back into the hands of the wireless carriers, rather than to benefit the end users.
