On the contrary, Messages is routing messages to Messages IDs, and it's kinda on you whether you use an ID string that looks suspiciously similar to your number.
This is incredibly easy to turn on and off:
https://support.apple.com/en-us/HT201349
To be clear, you can have an iphone with an SMS phone number and Messages, and not ever mingle the two. Further, you can have a SMS phone get your SMS messages, while Apple users with your number reach, say, your iPad. That's a valid use case.
In the situation you lay out above, where you forgot you didn't want to use that as your Messages ID any more, you can "de-register" if you forgot to remove it:
If only if it worked as advertised. I can turn it off as to messages directed only to me. But if a group text was on iMessage and I'm the only one who bounces off to Android, new messages to that thread will exclude me, EVEN IF I'VE DEREGISTERED MY NUMBER. I've tried this repeatedly. The only way to begin receiving messages from that group is if EVERYONE on the thread deletes the old thread and begins a new one in green bubbles. It ENRAGES me, and it's been the biggest barrier to me transitioning to a Galaxy phone. When I'm the only one on Android, I just stop receiving the messages to the legacy group threads. And there's no way I make 30 iPhone users all delete those threads. Apple could ask its own servers "have any of these iMessage accounts deregistered their number? If yes, force thread back to SMS/MMS." Apple does not do that, and thereby severely handicaps any effort to move away. I hate it and would happily support a class action to change that practice.
It’s not intuitive of course, but you can totally turn it off and deregister, even if you don’t have your iPhone anymore.
iMessage falls back to SMS within a few minutes if the message can’t be delivered. This often happens if the recipient doesn’t have a data connection.
When I've switched back and forth from Android on a few occasions I've had to have users update that contact card for SMS to work properly. I don't think its necessarily an iMessage issue more iOS, but if anyone is still having issues with the switch after de-registering, check that.
However, they do have UI on all of their iMessage programs, and on the website that you can get to from any web browser (on any brand of device) for your AppleID/iCloud account that can remove your phone number from your AppleID at any time. Then, after some minor propagation time, messages from Apple users to your phone number will no longer be routed to your iMessages account, and will instead be sent as SMSs.
So you have an option to tell Apple at any moment, even after you have switched, that you no longer want that number attached to iMessages. How exactly is that hijacking?
Since this is a technical community, and you're a technical person who presumably knows how iMessage / Apple's infrastructure works, can you explain if this is correct:
- I'm an iPhone user with phone number N. In Apple's system, I'm flagged as supporting the iMessage protocol. Presumably Apple has some gateway that routes messages, and this sends me down the iMessage route.
- I swap phones. I now own an Android device. I have the same phone number N.
- Apple's system is slow to update, and its gateway still sees me as an iPhone user supporting the iMessage protocol.
- All messages from other iPhone users to my phone number are routed incorrectly and I don't receive them until Apple updates its gateway to use SMS for my phone number.
If the above is correct, what would you call that? People who want to contact me have no idea what a protocol is, but Apple has impacted their ability to communicate with me. They think all text messages are the same, but this layer Apple has built isn't open or interoperable, and is additional friction for anyone wanting to switch off their platform.
It's very hard to excuse this behavior.