Thats good to know. I did wonder if once it has the weight of a mic on there it would behave differently.The desk part is like that yeah, it did confuse me too, seems like it should either have been made with a smaller bore or provided with a sleeve insert, however, once the arm is in there with a mic you really don't notice and it's nice and solid so I'd totally forgotten about that minor point.
I'll probably go with the through deskmount option anyway - its such a clean finish