Or did I make that up?

No such rule that I know of.

Here's the section from the Competitive Rules.

When acquiring a target lock, a player must first declare the intended target. Then, he measures range to the declared target to see if the target is within legal range. If the target is in range, the ship performing the action must acquire a target lock on the target. If the target is not in range, the player may declare a different target, or he may declare a different action.

Nothing like that in there.

so i guess my question is where are the competitive rules written down so one can confirm things that are said about it?

in the FAQ page 17 is the Competitive Rules section.

Also on page 17 of the FAQ it specifically states:

so i guess my question is where are the competitive rules written down so one can confirm things that are said about it?

in the FAQ page 9 is the Competitive Rules section.

Edit: My bad I listed the wrong page. Page 17 is part of the Q&A section.

Good for you but this is not Warhammer, and they put in premeasuring in Warhammer already even with fantasy (it is compensated by bounce effects and scatter dice). If you say there should be no premeasuring then that means you can only use the range ruler after you declared a target and an attack and if it is not in arc or say range 1 when using a 2-3 attack then it is like landing on an asteroid (you don't get to attack). If you want to do some sort of an ironman match with those kind of house rules then be my guest but you won't find me playing that game with those rules in place.

Now as for the game there are times when you are supposed to measure/premeasure (and should even if it seems a little redundant) and times when you can't and it is stated in the rules what are those times. The main problem here is the idea or statement "premeasuring is for noobs" or only players of lesser skill need to premeasure. This is just another example belittlement of other players who are playing by the rules that some people disagree with.

So I'm belittling players? Where did you see that? Probably the same place you got the non-existent "premeasuring is for noobs". I'm showing that the game would be a lot less exciting if we added pre-measurement, as illustrated by that Worlds match. They did allow pre-measuring in the rules for Warhammer a few years ago and, surprise, using any kind of artillery is much blander. You just pick your target and roll scatter dice.

I can see how you'd mistake my post out of context, but I am arguing in favour of how the rules are currently. There is no measurement outside of performing an action with the exception of immediately before deciding the currently active ship's attack. No need to have an "ironman match" to go by these rules - they're the standard for competitive play!

In a game like Xwing, being able to measure everything would be terrible. The times somebody may use target lock to "pre-measure" (i don't find that cheating, i find it like a perk for target lock) even if you thought that was cheating, don't outweight the lost of the guessing game which is Xwing's movement phase.

And yes, being able to measure eye balling is a skill that you need to train. What Rithrin spoke off, is not only about a trebuchet, but a 120cm range unit shooting a 90cm range unit which could not fire back even after movement, etc. Now that's ezpz, not to speak of how much slows the pace of the game systems.