I've read a lot over the years about setup stuff, and neck relief seems to be one of the many things that are debated in forums. An idea popped into my head, and I'm wondering if anyone else has thought about it or read about it.

It occurred to me that maybe one reason a bit of relief is recommended is not for playability, but because of the most common method of checking relief - the "string method". When checking neck straightness with one of the strings, the only way to be absolutely certain that the neck isn't back-bowed is for there to be at least some gap at the middle frets.

Regardless of opinions about the need for relief, or about the amount of needed relief, I think my observation might be useful.