I was looking around tonight and stumbled upon this:
https://www.bim merboo st.com/showthread.php?96803-Maximum-PSI-offering-forged-S55-pistons-and-rods-for-F80-M3-F82-M4-and-F87-M2-Competition]
(Remove the spacing)
If you scroll down enough you'll see the side of the s55/n55 rod on the right and there you'll see the parting line which does look pretty wide. And imo (not an expert so I still could be wrong) it looks like it is indeed a forged parting line.
So the stock rod looks to be a powdered metal factured-forged connecting rod.
SeanWRT my apologies for grilling you on your poor sources (didn't mean to be a dick before I just wanted to also get to the bottom of this with accurate information), but it looks like although that article was riddled with alot of misinformation it was correct about the rod.
Also if you look at the numbers on the rod and compare it to the n54 rod from my ebay link, they're different rods like what I stayed earlier. However they're very similar in design.