Memorizing the spymaster layouts was almost certainly not intended by the designers of Codenames. Probably someone realized it was possible, but as other commenters mention the increased friction of fully randomized layouts isn't worth it when almost no one will want to do this.
This is the most frustrating part of Scrabble to me. I consider my vocabulary to be pretty good. But frequently when I try to use an even slightly-esoteric word in scrabble, it turns out to not be in the official dictionary. And conversely, the official dictionary is full of words I've never heard or seen used by real people and often has some definition like "18th century slang for <word>". I then lose to people who know all these weird words (especially the very short ones, which they've memorized) and who admit they have never heard these words outside a scrabble context either.
In short, the English the players speak and the English defined by the official dictionary are different enough languages that it seems only useful as a way to learn "Scrabble English" and not modern English.
I was thinking more of remembering that the layouts have basic characteristics: a team's words are not bunched on one side, or all lined up, or in a circle, etc. Not your team's, not the other team's.
But now that you mention it, fully randomized would be easy to do as a phone app. And a phone could be propped up in front of the spymasters. (The setup with the layout propped in front of the spymasters works really well in a party setting, where it's normal that some people will get up and walk around without wanting to cheat.)