State registered and titled ≠ Legally federal registered and titled.
That said, I personally don't think you will ever have any problem driving your R33 regularly, or a R34 for that matter. There are at least half a dozen R34 GTRs in the region where I live, and they are out and about all the time. Just don't do something stupid like trying to file an insurance claim and your car will live a happy live.
Also I don't think you will have trouble selling your R33 after you are done playing. At this point it is pretty clear what classifies a fully federal legal R33/R34, and a buyer who wants to obey the law will do so by properly researching and understanding the law as it states and verifying if all documentations are in order. And for a buyer who thinks a non-federal legal R33/R34 is legal would believe it is legal, so there really is no point to contest despite what the law clearly states. Plus the legislative and executive branches are not besties. So there will always be these two separately circulating markets with each's own federally legal / non-federally legal cars and befitting customers.