-
Nothing that prevent it to take it apart if you really want to do it, but not necessary so why do it?
Once I get home I'll scan the instruction book that comes with the frame kit.
They even say that you could just use their steel cylinder as cutting guide, but I used a clamping guide for obvious reasons.Do you de-lace your wheel if you need to replace your hub bearings? :)
-
but not necessary so why do it?
For the reason you yourself identified - cutting produces a load of horrible carbon dust, which you want to keep away from the rest of the bike. That's much easier with the fork separated from the bike. Also, it's much easier to hold the steerer to make a clean cut if you're just holding 300g of fork by the steerer about 20mm from the saw blade, rather than trying to hold 2kg of bike by a grip that has to transfer the cutting load through the frame and headset. Ask any machinist - sound fixtureing is as important as anything else to a good outcome.
I still don't get why you would leave the fork in the frame while cutting. There's nothing about the Look design which prevents your removing the fork and holding the steerer properly while cutting, then you can clean up all the dust in a completely different room from where the headset bearings are stored before bringing the (now clean) fork back into the clean room for final assembly.