Apple Watch Ultra can't send sms by itself?

So Apple likes to hide this as I've only seen it in some foot notes or once you go searching support. Not a lot if anything on pages before buying and all the review sites seem to just never mention it. This is also the case for all cellular models. Even some exact questions of 'will it work by itself' people have incorrectly answers 'it even works if the phone is far away and switched off'.

Even though the watch has a cellular modem, either by software design or hardware limitation, it can't send SMS messages without the iPhone it's paired with being on, having a signal, and having iMessage enabled.

So if you leave the phone home and the battery dies, no sms for you. If you leave the phone locked in a locker at the gym where it has no signal, no sms for you.

I wanted to be able to leave my phone locked in a safe in my car when I go road cycling for a couple hours. No SMS capabilities. So I can't just send a quick message to let someone know when I'll be done or give a location update. Also can't receive quick messages.

Phone calls still work, but seriously, who makes a call when working out / running / cycling for just a quick 'made it to the half way point' update that only needs to be a single sms.

Unless I've missed something somewhere this is extremely frustrating. I'll probably just cancel the cell plan for it since I'm going to have to have my phone with me anyways it seems.