Yes there is a sleeve (tube) inside the mount rubber that controls the compression of the rubber when the bolt is tightened.
I would say that whoever made the mount just did not get the angle quite right to get even and symmetrical compression of the rubber. I would not worry about it at all, unless someone else here with more experience has a different view.
"The Magic Carpet"
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Jan 2020