Bug on double experience with crafting

I believe it's a rounding issue. My theory is that when you proc and do a 'double action' it actually is using a slightly different formula.

Like, let's say you're getting 129.5 exp when using 1 mat/action. It simply rounds it up and you get 130.
But for 2 mats/actions, maybe it's taking that 129.5, flooring it (cuts off the decimal), and then doubles it. So you get 129 * 2 = 258.

So, it's not technically a 'bug' just a formula discrepancy. I'm sure Vysn can confirm/deny this theory when he has time!