75hz LCD Monitors

I have a 120hz monitor (Samsung S27A950D) and it spawned a discussion about refresh rates with my friend. We were talking about how many monitors are able to accept a 75hz input signal, and were debating if that meant the LCD was actually operating at 75hz or not.

I know that the default video mode used when you boot most pre-UEFI computers is 640 × 400 @ 70 Hz, and that even includes the Windows Logo pre-Vista. So obviously an LCD will need to be able to accept a signal of at least 70hz regardless of what refresh rate it actually operates at. I've also had LCDs exhibit strange behavior when set to 75hz in windows.

But my friend really wants to believe that 75hz means the monitor is actually refreshing 75 times, not just accepting the signal but still operating at 60hz. Can anyone shed some light on this?

The over-60Hz LCD Thread

How to test how many Hz an LCD monitor is really displaying

I tried forcing my u2713hm to 75Hz via custom resolution in NVCP, and while the monitor OSD displayed the input as 75Hz, I'm pretty sure it was still operating at 60Hz. The frame skipping was obvious in Tribes Ascend (very fast paced game). There was a consistant stuttering that went away when I went back to 60Hz. But maybe it's not as simple as trying to force a custom resolution in NVCP. I haven't looked that much into it.