its not abusing a loophole. if something isnt in a state for more than 50% of the calendar year the state should have no claim to it. its a federal matter at the point cross border taxation IMO.
I mean you do have to live close to a (tri-)state border to pull this off, but it’s probably doable.
As a reminder, we’re talking about a (hypothetical) 183-day rule for car registration here (as opposed to the ~30-day one we currently have, which makes loopholes that we discuss here absolutely impractical).