""House of El? What's the House of El? If he came here as a baby, how does he know what his parents' crest was? Why would his human mom put that on a costume? Did she know about Krypton? How did she find out? Memory matrix? What?"
Not as simple as you think - it's just that, unlike Wonder Woman, it's enough a part of the popular consciousness that no one has to ask. If she could get, I dunno, a movie or a series or something... ;_;"
Yikes, this is a reach.
NONE of that stuff is even slightly necessary to get the sentence explaining the house of El crest. Not a bit of it. Memory Matrix? Are we being serious, here?
But even people with some history with Diana wouldn't know what the sentence with Diana referenced. It answers no questions, just raises new ones.