Inquiry about planned order for planning factor 0 item

Prouduct family ATT.WMOM*A5U has product family memebers ATT.WMOMA5U and ATT.WMOMA5Y. ATT.WMOMA5U is the prime part with planning factor of 100, and ATT.WMOMA5Y is set as planning factor 0. ATT.WMOMA5Y is set as a substitute to ATT.WMOMA5U (the setup is attached here). Demantra sends forecast at product family level to ASCP, and planning will be based on planning factor. After ASCP ran, we found 0 planning factor ATT.WMOMA5Y got planned order. To make this item not to have planned order, we have to set create supply flag for this item ATT.WMOMA5Y at item master as N. Is the reason that ATT.WMOMA5Y