Interesting, Matt. My view would be: test the guitar for yourself and see what happens. Try taking all the strings off and then timing how long it takes for the new set to stabilize at correct pitch. Then, the next time you change them, do one at a time and run a similar time check.

I certainly don't think it hurts to take all the strings off for the purposes of doing a decent cleaning job on the fingerboard. But I would only do this when the fingerboard really needed it.

Most modern guitars have truss rods - some double rods - but many necks on old instruments stayed straight and true prior to their introduction. I have a 1904 Windsor tenor banjo with no truss rod but a V-neck construction, and it's as straight as the day it was made. A friend of mine has an old Gibson Kalamazoo from the 1920s, and the V-neck construction in that guitar is just as good.