What always drove me nuts about this episode is it was previously established going faster then Warp 10 was viable in overload conditions (See Star Trek 1) and reinforced else where.
The theory-held that Transwarp was simply pushing off another form of substance gradients that essentially allowed for more efficient and thus potentially faster warp speeds.
The theory, as I understood it, up until "Threshold" (S02E15) was going beyond Warp 100 is what gave you crazy effects as seen in "Where No One Has Gone Before" (TNG S1E06).
Voyager's whole Warp 10 ordeal kind of just shattered a whole bunch of heavily implied in show references and a whole bunch of written reference material over the course of the few seconds they broke warp 10 and things kind of "exploded".
I have to admit, I have a big grudge against Brannon Braga (writer of this episode) for basically throwing a whole bunch of martial out the window, not even referencing any scientific material on the topic an coming up with something that REALLY makes no sense.
Wait a sec - Braga got the warp 10 = infinite velocity thing (as dumb and contradictory as it is) from the warp speed charts in Mike Okuda's TNG Technical Manual and Star Trek Encyclopedia - the very same ones you were saying should be 100% canon in the "Intrepid vs. Galaxy class" thread.