A guitar's design shouldn't be at least enjoyable enough to make the guitarist a better player?

I don't think we've been talking about guitars.

Only if you missed the part that this technology tries to capture "the spirit" of the creative side of the coder which is an universal, hence my analogy with making "the coder feel like a rockstar".

I asked "Is there any evidence for" the claim that "Devs code better products if they enjoy using the tools."

So far nothing has been offered.