It sounds like glonass is assuming that atomic and solar time align to within 1 second?!

I don't get it either. A one second deviation in satnav is miles, right? I don't understand how the system could function if it assumed that UTC was TAI.

This probably explains it once I can drink my coffee:

https://berthub.eu/articles/posts/leapseconds-expose-bugs-even-when-they-dont-happen/

[Edit] apparently yes GLONASS just uses Moscow wall time. I don't understand how that works at all.