I haven’t heard back from support but it does seem to be a Zwift on iOS thing, or at least on iPad.
On my lunch break I started a ride on my Apple TV and did a quick 3k, in jeans and sneakers. Saved and exited the game and when I went back my total was showing 1.9/112 so that was working at least.
I’ll try on my iPhone after work at see what happens then.