Really? That's odd. I learned that particular rule in Warhammer Fantasy, and you should have seen the flame wars over on the Warmachine forums when PP decided to allow unlimited measuring from your warcaster. GW games were always the most restrictive on measuring, and some of the last to convert to allow premeasuring.
For gamers coming from other wargames, any form of unapproved measuring is outright cheating. For example, if you have too much measuring tape out, or you're using a ruler, it's expected that you leave the extra behind your model. If I'm moving 4" but my ruler measures 12", and I happen to put the full 12" ahead of my model, that's cheating.
Not in any war game I've ever played or seen played. About 10 years of 40k.
I won't guarantee that your experience is necessarily the minority, but here's at least one nice big citation for "It's cheating":
I won't guarantee that it's in the majority either, but it does seem ridiculously retentive to me. It should be noted that the BoLS article generated, shall we say, a lot of discussion on the topic. I suspect it is more how exactly you are using it. If you have an extra 3-4 inches of measurement and are clearly moving things quickly and not looking past your move distance it would be fine, if you have 24" of tape measure out and are spending 2 minutes moving each guy, which just happens to be directly in line with a likely target, then yeah problem. Basically, yeah, premeasuring improves most war games (but not, I think, x-wing).
Not sure if this has been awnsered or not. But as far as i can tell post 6 ED 40k u can premesure when ever and what ever u want.. Premesure shots, move, psychic powers, everything. But hey this isnt 40K.