Sure, they could do that. But once again, I must ask: How is making an SMS Android app in 2024 good for their business or valuable to their existing customer base?
Well, if secure communications is what they're customer base is interested in, it would make sense to provide them a means to use Apple's app to communicate securely with their Android friends.
[best Don Draper impression] That's what the regulation is for!
It obviously isn't in Apple's business interest. Regulations primarily exist to force companies to work in the consumers interest even if it's against their business interest. If every regulation was in line with business best interest there wouldn't be any point making them.
Well, if secure communications is what they're customer base is interested in, it would make sense to provide them a means to use Apple's app to communicate securely with their Android friends.