I guess they are 'seeing' something in their mind's eye they've already experienced and they can't distinguish it from what is really going on.
That's what I was thinking. Something like that. Of course, it really depends on the writers and their understanding of concepts like 'subconscious,' 'unconscious,' 'repression,' and the like.
However, this page from Action # 839 seems to give the most insight as to what is happening in the story.
He genuinely seems not to know. He questions whether or not it was 'repression,' suggesting that he may have wanted to be able to live as an ordinary man but he also hopes it wasn't that but does not come to repression as the ultimate conclusion. Instead, he claims, 'he may NEVER know.'
This would indicate the phenomena does not have a definite explanation, but at the very least Superman and by default the writers believe that it is possible for people to surpress things w/o their conscious mind being aware. It could also indicate that the phenomena is something unexplainable by normal psychological/ physiological stanadards.
I think it is clear enough to say that SUperman did not
or
At the very least, whether or not it is possible to 'subconsciously' repress something in real life, in the story any sort of repression would be a subconscious act based on what is in the story itself.