I think you make a great point. Still, the insidious way that Apple introduced iMessage is something right out of the "Embrace, Extend, Extinguish" playbook that feels fundamentally wrong to me:
1. 15 years ago everyone in the US just used SMS to text between cell phones.
2. When iMessage came out, it wasn't like "Switch to iMessage!" Instead, it just was the default texting app you used with iPhone. So it replaced an existing, open standard with a closed one, but in a way where 99.9% of people didn't realize it.
3. In true "embrace, extend, extinguish" fashion, Apple added a lot of features to iMessage, but also didn't totally exclude Android users, but just made it seem to iOS users that when they got crappy photos or messages that randomly wouldn't deliver or crappy emoji responses "it was Android's fault".
Everything about the iMessage tactics (including getting teens to bully other teens for an out-group bubble color) is from the worst part of "protect the monopoly" playbook. Almost regardless of the legal nuances, I'm shocked when I hear anyone's broken logic trying to defend what they've done from a consumer utility perspective.
(One side note, yes, I fully know the situation outside the US isn't comparable due to the high cost of SMS in the late 00s in other countries that forced a migration to WhatsApp, etc. earlier. That still doesn't give Apple a break for their monopoly-preserving tactics in the US).