It's been this way in Pennsylvania for as long as I can remember.
Same thing in NY.
When I moved to WV, they charged me sales tax on a used car that I owned and had already paid sales tax on in NY.
I bought a new PU truck in NY to help with my move but used my WV address. That way I got a set of transport tags and only had to pay the WV sales tax which was less than that in NY.