I had one fitted to my import, you are correct they do specify they are not designed for JDMs, mine was fine, tips were slightly out of line but this is common with aftermarket exhausts and not really noticeable.
As long as you take it to performance garage that no what they are doing you shouldn't get any problems, at worst the fitter may need to remove the heat shields.
It is a really quiet system though, IMO needs beefing up with high flow cats and a pop charger or similar.