You're not following the line of argument. I'm not assuming a nonstandard sense of "fit." You are. I was only trying to make explicit what you've been implying.

To see that you're doing so, you need to define the objective sense of "fit" that would account for how a round peg would fit into a round hole, whereas a square one wouldn't. You need to define the word without assuming there's any outcome that's especially pleasing or normative, such as that the peg has to pass all the way through the hole. And you need your objective sense of the word to rule out a cube fitting into a round hole.

You're the one who tried interpreting Vervaeke's claim about natural harmonies as being objective, so you're the one who has to make good on this objective sense of "fitness."