When comparing two ciphertexts A,B a FHE sorting function will output a sorted pair of two new ciphertexts:

E.g. FHE_SORT(A,B) -> (X,Y)

where Dec(X)<Dec(Y)

But without decoding, there's no way of knowing whether X (or Y) comes from A or B.

Source: II. D of https://eprint.iacr.org/2015/995.pdf