Yeah I re-read post #64 in that thread and I think you might be right... there does seem to be physical variations to the JBBF units between say an "L1" and an "M" variant. I was skeptical since all JBBF 3 have the same part number... and it shows interchangeable between 135i and 1M. However, the pictures show there are difference in the relays inside of the JBBF. So... pretty much everyone who said they got this working without the "M" variant was just feeling placebo???!!!
I guess I am on the hunt for a JBBF 3 stamped "M" now. Seems to be the smoking gun.
If you go back and look at my post, it shows the M stamp. I don't recall ever changing it, perhaps because I'm E93.