That's odd. You should be able to change refresh rates with no discernible change in quality...other than flicker.
The trouble is, that when a monitor is made with say like GG's 1920 res then that highest figure will be the Native Resolution. Getting back to a work-a-day line frequency is destructive to the focus/registration because the scanning rates are just not acceptable to the size of the light-generating clusters.
I've found an old thread with some comment about a Samsung 22" Multi-synch. In the old days, the use of that term was a definite indication that it would multi-synch. To clear up a point...of course, if it's locked on, it will be multi-synching. But the timings are unacceptable to the LED sizes in all but the true ones.
One will phone Samsung in the morning.