Wheel/ Lift Installation Question

Dident know whether to put this in tire/ rim or suspension section so I just put it here.

So im getting a 3" suspension lift, 16" kmc enduro rims and 285 nitto trail grappler mt put on my 2012 trd offroad. It was being installed to day at essentially offroad (I bought everything but the rims there) in Tennessee and they called saying to get the rims on they would need to add some wheel spacers because of clearance or something like that. Does anyone have any idea why? I have not heard of this happening with this rim before. I went ahead and told them to put the spacers on because I need the truck back this weekend but does anyone have any information on why they did this?

Any imput would be helpful! Thanks.

 

hitting the UCA's?

 

Most likely not clearing the UCA's. As stated above^^