That patch set does not implement transparent creation of 1GB mappings. It also contains dubious things like this, which make me think the branch was a WIP: https://github.com/Seb-LineRate/freebsd/commit/66a8d3474d410...
The only mailing list thread I see regarding this is here, and it doesn't seem particularly underhanded to me: https://lists.freebsd.org/pipermail/freebsd-hackers/2014-Nov...