I have seen groups of women and single women cruising solo. I agree with the OP. When I cruised "basically" solo in May I could tell that the dynamic was different from when I cruised with my wife. People did look at me differently and with much more "caution". Once I whipped out the wife and grandkid pictures I was more accepted.
I have also found it interesting that when I have cruised with my nephew and son-in-law we were automatically categorized as a gay couple cruising together. Nothing wrong with that but that assumption was incorrect and we had to correct a number of people.