ffmpeg -to option acting like -t option? The following command is producing a video of the exact length of the -to parameter:

ffmpeg -ss 00:06:26 -i fftestinput.mp4 -to 00:06:38 -r 29.97 fftestoutput.mp4


Again, the final product is a very nice video of length 6:38.
Yes, it does. -to looks at the timestamps. And input ss resets them to zero from the seek point. Either use -ss as output option (after -i) or calculate and use duration -t. The former will slow operation, as it performs a slow seek (decode and discard till inpoint).