Watson was married more than once. He was quite a ladies man. Holmes was not romantically interested in Irene Adler. He just recognized her as someone her as someone who he didn’t outsmart.
Are you sure in the current BBC version, Holmes wasn't romantically interested in Adler? He did save her life.
In the current CBS take, Holmes' thought-murdered GF Adler turns out to be Moriarity.
FWIW, In a Rathbone/Bruce voiced [US] radio epi, the retired Holmes visiting retired Watson is the object of a successful con by Adler's adult daughter.