Grips axis bars are screwed together.
Other BM models do have a solid axis bar as deathofallthings said.
There are many other factors that could explain the reason for a different feel.
Again, as deathofallthings said, the liners may not being parallel, coatings will make a difference or the liners edges are a little sharper on one more than another.
All duplicate pieces, are just that, duplicates. Not identical.
One piece was produce on Monday when the jaws and bits of the machinery were fresh and new.
The other on Friday the last day of production before doing a breakdown, cleaning, adjustment and set up for the next week.