Hi, I've grown some orange and lemmons in the past. They never really develop any really fine fiberous roots. They do seem happy with the somewhat larger sparser roots, no problem just the nature of the trees.

Bob

I used 100% turface / napa floor dry on a calamondin tree, I just repoted it after 3 years and had it in a 1 1/2 gallon clay pot (not glazed) and it was one huge fiberous root ball. I live in florida and have kept the plant outside at all times. Ill try to get some photos up of the root mass.
You may want to switch soil types.