When you are talking about derating and bundled cables, neatness is your enemy. You really want them to be very disorganized between holes. You want the "inside" cable in hole "A" to be outside in hole "B". I really don't start thinking about derating unless I see a very pretty bundle with carefully aligned cable bundles. The cables in the middle are cooking. If you fan them out between holes they can breathe.
I have seen inspectors make the same demand in large panels that were a thing of beauty but they had big bundles of THHN going more than 24". The EC almost cried when he had to cut those tywraps and spread the wires out, "messing up" that panel.
