Updating Apple Watch with AT&T fast data over cellular (as I can do for iphone and ipad - fast and easy)

Why is updating Apple Watch limited to wifi? I don’t have wifi available currently and use my AT&T Fast Data over cellular hotspot to update my two iphones and ipad Pro — very fast and a far bigger download than the Apple Watch update would be. Plus my Apple Watch cellular account is through AT&T just like my iPhones, so my Apple Watch with cellular is on the ‘same network’ as my iPhones. Limiting Apple Watch to wifi is terribly inconvenient and suggesting we use a public wifi network to update is unwise and unsafe.