#there are maybe a few that show him as an embryo/fetus (including the lower part of the one above)

[isfjmel-phleg]

In Superboy 1994 #0, Kon is being examined by Professor Emil Hamilton, who asks him, "Tell me all about yourself, from the beginning! Yes--that'll help context the data..."

"My first memory?" replies Kon. "You won't believe this, Doc, but..."

His first memory dates from while he was still in development (although already physically a teenager, judging from his appearance), and...

Kon's first memory is hearing the word "mother" said. Not regarding his own mother--he of course doesn't have one--but in the context of a joke in a cartoon show that Cadmus wants him to know about for some reason.

This is followed shortly by Westfield (his human DNA donor, pre-retcon) calling him "son" while identifying him as a pawn in Cadmus's scheme to create their own mind-controlled Superman.

Therefore, his earliest memory is of being exposed to distortions of parenthood. "Mother" is a punchline on TV, and his "father" plans to exploit him.

This explains a lot.