The Linux version will work at 50fps (or slower) unless you are using fast forward. In that case it will (for 'g') go 8 times faster or (for 'v', available onyl under Linux/UNIX) as fast as it can.
The Windows version is a little more dodgy using the Windows event loop and Windows 3.1 compatable timers to control time and flow. It sets the timer to 160ms (since it's only accurate to 55ms traditionally) and uses call backs to perform 8 frames. This should work fine and give 50fps. I have had no problems with the game going at 50fps (or slower for slow machines).
I assume you've got these stats from the recorded game files (?) which record the average frame rate for non-paused game play. My games are around 50fps when I don't use fast forward. My last game was 56.89 fps, but I started the level using the 'v' key and died pretty early.
Hope that helps. I can only assume you use the 'g' button to speed up things and avoid waiting. If not can you tell me your system details (OS basically).
Well, one for 1000 pointer to get!