I can see your point of view, and it is a valid one! If you were my GM, you would probably make that a ruling and I'd happily abide by it.
But, in a world of magic, I can think of a lot of fluff reasons why this seemingly 'illogical' (to you) conflict between living and inanimate objects exists. Maybe the permeation of ectoplasm through a living being (with essence) enables the power to work, but the non-living thing has no essence, so it can't. Meanwhile, I've already presented a reason why the devs might have decided to place a restriction on movement for inanimate objects (my previous towel example) but given that the expectations are already set for living beings, they didn't have to spell it out. Which can go both ways! I.e. OF COURSE they can't fly, humans don't have wings; or OF COURSE they can fly, it's one of the spirit's abilities.
So, once again, I appreciate your vehemence against flight, and respect your perspective as well as see how you are getting to it, but it doesn't resolve what I'm actually looking for... which is the no shit, unambiguous, black and white source stating the case. Which I think doesn't exist.