I noticed that as well when I did my ZCP conversion. I tried pulling the PNs on realoem to compare them, but there are about a half dozen different spring options per model, so realoem doesn't bother listing them.
'09 E92 M3: Space Gray, Black, Carbon Leather | ZTP 2MK ZPP 2MT 6FL | link 1 / link 2
Mods: M Performance exhaust | ZCP retrofit | Euro airbox | GTS DCT flash | JPN 240 ECU flash | Euro LCI taillights | CRT lip | OEM alarm retrofit | Space Gray bumper plugs | BMW Performance: Mk. II spoiler / Mk. II non-electronic steering wheel / mirror caps / front grilles / side gills / intake louvers / emblem