Sengir didn't nerf bronze, that was a rumor that got disproven by DrRed in post 15,283, a little ways up on this page.
The wiki could easily be out-of-date, so I'm not going to accept that as disproof. (I haven't verified it either, it's just a rumor to me as well)
P.S.: I really hope that lava centrifuging isn't one of the reasons that GregTech keeps the bronze recipe at half output. Lava centrifuging is an absolutely stupid mechnic and it's the first thing I disable when setting up a new game world. Seriously, how does zero-effort infinite metal even fit into a mod which aims to make things more complex...?
As Greg himself put it, GregTech is absolutely about making big factories. You spend less time mining for not-so-valuable metals, and spend more time setting up 50 centrifuges and magma crucibles and their power supply.