Wiring – Should an optical cable inside a house be run in conduit

The derating would only occur if there is a section 24 in. long or more, where the cables are "bundled" together (from my understanding).

"without maintaining spacing for a continuous length longer than 600 mm (24 in.).

If the cables are run through a joist cavity, they'll be "bundled" for 1 1/2" - 3" at the top plate, and 1 1/2" - 3" at the bottom of the wall. Each of which is far under the 24 in. limit. Where the cables dangle through the cavity, they are not wrapped, taped, or bound together. They are only "bundled" for a short distance while they enter/leave the cavity.

This sounds like an exercise in frustration. Even if you do manage to bond the wires together strongly enough, you will surely damage them by pulling them through staples or around corners. I have frequently seen damaged cables from being pulled through tight spaces. If you damage the outer sheath of a coax cable you will lose a lot of signal strength, and if you damage one of the wires in CAT cabling you will not get any signal at all (or it will drop down to 2 pairs instead of 4).

If you are really insistent on trying to pull the cables through without opening up the wall (which is probably what you'll have to do in the end), try this: get some tough wire pulling twine and tie that to the end of your old cabling. Then when you're pulling the old cable out you will pull the twine along to replace it. This will give you an opportunity to inspect the old wiring: if you damaged it pulling it out, you will surely damage the new ones going in. If you were able to get the old wiring out successfully, it will probably be easier to pull the new ones through with the twine since there will be less resistance. However I still think this is going to be very annoying and you'll never know the condition of the cables.