Well, I don't go to that site much anymore. Last I checked, it was still using uncompiled scripts for the install process instead of SSRs, and the only firm it installed was B9S (no GM9 option). Does it have you restore a NAND backup? If yes, you will be on whatever version that backup was on. If no, and it only has you run d0k3's script for returning to retail, then it will be on what it is on. Roughly 99% of your system is on retail 11.6 right now. All that script is going to do is make it 100% by overwriting your firm partitions that currently contain B9S with whatever version of NATIVE_FIRM is on your CTRNAND partition. If you're running 11.6, that would be 11.6. There is no 11.2 on your NAND for it to restore if it wanted to (as of you updating, it's gone). Only restoring a NAND backup or manually downgrading using something like SysUpdater with update files grabbed via something like 3DNUS will lower your system version. Hope that explanation helps.
I wouldn't recommend doing this for no reason. I've done it quite a bit recently, but I was working on install scripts for an AIO that encompasses installation and customization. I needed to make sure they work correctly on various firmware versions and won't brick a device. It would be irresponsible to release something like that untested, after all. Especially with me having both a hard mod and NTRBootHax. I've got no excuses, being setup like that. I've not bricked my system once while doing all of these tests, but however small the risk, it is there. I would not advise taking it needlessly.