From what I have experienced is that even with a smaller ET size yes the wheels will fit and as said closer to the inner wheel arch, which is ok the only issue being is that the brake caliper can rub or even not allow the smaller Et wheel fitment, as it touches on the outer inside rim of the different wheel being fitted with a much smaller ET size, if I my explanation was ok, if spacers are fitted as you most probably know it moves the wheel centre furter out and so does not foul on the brake caliper, the rear's have more clearance, I also had to get different length wheel bolts as depending on the wheel hub being fitted may require either shorter or longer bolts as mine came through the car/brake disc hub and caught on the other side of the car hub, I careful spun the each wheel when fitted and bolted up to check they spun freely when changing my wheels making sure also I had a good 8 turns in before torquing up, This is just from my own experience, wheel choice will make it different for whatever wheels you choose but can see why they suggest spacers or spigots if that is what they are called on the car hub be fitted in relation to catching on the brake calipers. A case that even if the wheels may seem a good price at the time you buy them, have a go at how they fit before you part with your pennies if possible and you will know to add whatever cost of bolts and spacer thingies if required to the shopping list.