I'm not sure about SS TDR but according to w2aew it's the fast edge that's important.
He uses a 74AC14 (because it has a fast 2ns edge) as a 6KHz pulse generator with 50 ohm resistor in-series into the cable under test
WRT TDR range, he said in another video, that TDR will only work on cable with a parallel return path (not sure how he put it). ie. coax, twisted-pair, romex, etc. I assume more of the signal is lost in the unshielded cable therefore less range as it is harder to see the return signal (having less amplitude).