@Captain_Nik has it - I was accessing this using Safari browser on my iPad. I just tried it again and indeed you can scroll to the right. However, by default on my iPad, the UI shows up with almost precisely the right # of pixels for SIM A and B to show up, so there’s basically no indication whatsoever that other SIMs are hidden to the right.
This is super frustrating as well because I’m no longer in the campground where I was having an additional problem, which [Edit] I’ve posted a new thread about