It's the design rather than the material, to allow the rear block to be flipped and change the antisquat the holes are drilled
slightly oversized and the hingepins sit in the holes at an angle.
This is good because it lets you use the same blocks yet still have different setup options, but means the contact area between the pins and holes is a fair bit smaller than usual so any wear will be faster. If you threadlock the hingepins the blocks will never get sloppy
