Water Bottle Mounts

Bianchi Boy

When I picked up my 07 Scott CR1 Pro I noticed the the water bottle screws on the seat tube had washers of about half a centimetre thick. The ones on the down tube didn't. I could not see any reason for this. I have fitted my carbon cages directly to the frame on both the seat and down tubes OK. there is no fouling of the from mech at all. Has anyone else noticed this, or were these washers there for another reason?