The 67 timings are a bit more relaxed than on 197s - they're slower to get going from a stop, and their dwell times are usually slower than as well. That said, looking at those timings it's clear that the 197 was in super power mode - this isn't necessary for normal 197 timings but it will help when running late.
67s are hardly sluggish though - they'll outperform even a 175 which before the new fleets came in were the fastest units in the TfW fleet - but a fully functioning 197 on super power mode is next level. If it had been a 3 car it would probably have made up even more time.