It seems you’re implying these signals are accurate, that this increased thought leads to actually more useful phrases. We’ve then adapted to remember these phrases more easily.

I don’t think that’s the case. It’s easier to remember all sorts of rhyming things besides advice. The article explains the semantic narrowing that accounts for it. “Blue shoe, red bed” is going to be easier to remember than “Green shoe, white bed”.

I actually take rhyming advice as a strong indicator of low quality. It is much, much easier to come up with a rhyme than to accurately find the effect, if any, between drink order and hangover. But, the rhyming sticks in people’s heads. This gives it a free pass. Non-rhyming phrases, non-beautiful phrases, have to survive on their own merit.