Ah, got it. I thought you were still talking about the Play Store there. It's telling that I didn't even categorize Whatsapp that way instinctively, though.

I think maybe because I also don't think of SMS as a "first party" thing, since it's a pre-existing standard, not an Apple or Google thing at all. In my mind SMS is a public service thing, like AM radio, and messaging is a completely different application.

It probably shows how successfully Apple appropriated it in the US, which I admit I keep forgetting.