Yes, I think it's an appropriate parallel with the "people on the pavement" question years later. The difference, I think, is the level of Ennis's own self awareness. At this very early stage at the end of the '63 Brokeback summer... his question "what are you looking at?" is something that we as viewers can hear as multi-layered... But, in Ennis's own head at the time of uttering it, he probably doesn't intentionally mean that question to be introspective or about his personal identity. In his emotional state, when he blurts that out, I'm sure he means it to be taken exclusively at face value by the passerby as a "mind your own business" type of statement. But, we as viewers can hear that question as almost a literary device... that can mean a lot more to the audience than to the character himself at the time.
Later with the "people on the pavement" conversation with Jack, I really do think this is a fascinating moment when Ennis is revealing that he may have more self-awareness about his sexuality than he normally lets on. It's almost like he's taking a slight step back from the early "I'm not queer" declaration. By wondering if people on the pavement are looking at him (and Jack) like "they know"... without actually saying the word "gay" or "queer" it's pretty easy to fill in one of those words into the statement.... "like they know...[we're queer/ gay/ different, etc.]."