I feel like it is though. I mean actually it's possibly one of the most difficult Pokemon to obtain as you need to trade it with someone else WITH an item. Getting the Up-Grade and Dubious Disc is (sorta) hard, and you need to get lots of BP for them IG, but if you have Global Link, you can just play the Balloon Pop Game, and both of the items are available there. Although its very rare to get them, especially the Dubious disc, so overall Porygon Z is more DIFFICULT than RARE to get. Be proud if you do have one as you went over one of the most difficult evolutionary line.