iPhone 15 Pro 17.4.1 and iWatch Series 9 10.4 inconsistent sharing of Alarms - why?

2024-05-11:

I never know if alarms will synch/share between my iPhone 15 Pro running iOS 17.4.1 and my Apple Watch Series 9 running iWatch 10.4.

Some alarms sound on both devices simultaneously, some only on the iPhone and some only on the watch.

Why such an inconsistency?

I have deleted and set up the repeating alarms multiple times so please don't suggest I do that for the umpteenth time again because that strategy does not work.

Why is it so bloody difficult to set up an alarm that will go off on both devices simultaneously and why do some alarms work correctly and some do not?