Q.potted lemon tree
I have a potted lemon tree that has many very small feeder roots on top of the soil. It was like that when purchased. Do those need to be covered with soil? The graft is about six inches above the soil and these extremely small feeder roots. I have transplanted the tree into another pot, but did not add soil to the top of it.
You could certainly add a small layer of potting soil to just dress the top of the soil.
Here is a link with care instructions of potted lemon trees.