GPS and GLO time will be different for two reasons:-
1. Any UTC offset that is applied in the scenario because GPS time is continuous but GLONASS time resets to align with the UTC second count. This means that in the real world GPS leads (is ahead of) UTC and hence leads GLONASS. In simulation if you have a non-zero UTC offset GPS will be ahead of GLONASS.
2. 3hrs due to GLONASS being with respect to Moscow time but GPS is with respect to GMT (Moscow is +3hrs ahead of GMT)