Two Series 4 watches, one cell, the other WiFi, will both work with same Iphone

I'm trying to find out if you can have a WiFi and Cellular Series 4 Watch attached to the same Iphone and both would work at the same time, without one cancelling the other out.

AT&T said yes you can have two cellular watches attached to the same Iphone #, but whichever one was in use would cancel the other out. Since she needs the cellular watch working for the fall detection, I started wondering if you could add a WiFi watch to the Iphone with the cellular watch on it.

Anyone know if the watches will still cancel each other out if the other is used? I have a feeling the answer is no, they'll keep cancelling each other out (and since I'd use the WiFi watch constantly to listen to books at work, I need a way both will work).

Thanks!