I thought the sports grill was a modification for all IS No it wasn't. Lexus accessory catalog just shows side-skirt kit, rear spoilers, illuminated sill plates - I don't think it is standard on the sport model Yes it was like the tints, LSD & lowered suspension, perforated pedals etc.
Maybe the sport grille does look better - but I think the point I am making is that the grille was about the only thing that distinguished a sport at a glance & it reminds me a bit of when loads of standard Minis were tricked out as a Cooper S. As a principle, mods to make a car look better to you are fine, but sorry, fitting bits which tend to make it resemble another model doesn't seem right. However, that's just a personal view which I am sure many don't share.
All the sport models I looked at when I bought mine had the same standard grill as the base model. I had to put the sports grill on myself.