Yeah the stuff about the batting end is crap, but the speeds for the fast bowling competition were done over the length of the wicket. That is, the time it took for the ball to travel the 22 yards to the stumps. Speed measurements today are done differently, it's based on the speed the ball is released at, and it's clearly documented in any detailed speed gun replay that the ball drops off in pace a huge amount as it travels, obviously enough.
So yeah, I'd say the measuring system that Thommo, Holding, Lillee, Imran etc went on was considerably less friendly to fast bowlers in terms of clocking high speeds. The fact that Holding and Lillee, both recognised as extremely quick bowlers at the time, both measured in the low 130s should tell you enough.