Why is OM_DEMAND updating non-inventory products?

Hello,

we have begun using non-inventory products along with inventory products. We find that when running the OM_DEMAND process, the non-inventory demand lines on IN_DEMAND set to status 20 are getting updated to cancel, 90. Wondering if anyone else encountered this issue and how to resolve. We understand the mark line for billing updates the non-inventory IN_DEMAND lines to 70 when run but our OM_DEMAND process runs hourly - thus happening before the mark for billing job. Thanks.