they resprayed the lower. that is not right if it was supposed to be brand new, the lower should be the natural black plastic finish, this is what makes it somewhat abraision resistant. technically the lower textured part is unrepairable for that reason, although some will try & repair it, the results your seeing is why it shouldn't be repaired really.
I can tell you that when I get these things new from infiniti sometimes the lower textured area is already scuffed up from handling in the dealers parts department & delivery, etc. I've had to return several when they come in scuffed up, it's possible they did put a new one but they resprayed the bottom because of a few blemishes from transit.
it can be hard to get a perfect bumper even when you do order a new one believe it or not, that's why it's impossible to get a good used bumper, it will be scuffed at least... the bodyshop should have refused it or returned it & ordered another, but then they would have delayed the job too... they probably made the call to just spray the bottom scuffed up area with bumper trim black or similar to just get it done & out... again, not right when you're paying for a brand new bumper which shouldn't be that way...
the other possibility of course is that they fixed your old bumper... if that's the case then there really screwed up...