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You're talking about the combination of fork length and BB height.
Track bike's BB are very high, between 5 to 10mm higher than road.
Mean a 140mm headtube feel more like 135-130mm.
Plus, the fork on track bike are typically short, so the headtube actually felt a little lower than 135-130mm on top of the BB height.
CX bicycles have says 135mm headtube but because the fork is nearly 30mm longer (395mm vs. Track 367mm) the headtube felt a lots higher than 135mm.
edscoble
Remember with reach/stack numbers that a larger size bike measures reach higher up the "virtual" headtube so even if the numbers are close the larger size does have more reach at the point where you place your stem.
Does this make sense (I can make a crude drawing...)?
2cm more headtube at 73 degrees gives ~6mm "less" reach
75 degrees gives ~5mm less reach
tldr: the difference between size 50 vs size 52 "effective reach" will be about 4mm more than you expect....