Considering the RDA deck + battery tube are machined from a single piece of stock with no welding visible in the well/deck area I'm pretty sure it was bar stock. There would be a viable insert welded or screwed in otherwise.
No, You reduce the end and use the hole for the positive contact.
I used to own a machine shop.
It's possible they use bar stock, but that would make them the most wasteful shop I've ever heard of.
There is no advantage, only waste.
Wasted stock, wasted time, wasted tools.
I actually like it, but don't believe the shop is that wasteful.