I think that step is to visually mimic the BBS design where they scoop out material in the spokes to make the wheels lighter. The scoop catches light on BBS wheels and these casts (and other) wheels fake that sliver of a highlight with the slim step behind the spokes. IMO.
Price shipped to 32707 for 19" in silver for a LCI e90 please.
2015 Raven Scion FR-S
2010 Black Sapphire Metallic 335i - Sold
2006 Quartz Grey Audi A4- Sold