QF gave me a status challenge last year, but they suggested I go for the Gold option, as they weren't convinced I'd be able to achieve Platinum with QF. I was surprised, as I had earned something like 5,500 Velocity SCs over the previous 3 years. They said they consider Velocity Platinum to be pretty much equivalent to QF Gold. It seems that when they evaluate your travel history, they exclude any SCs acquired through Family Pooling and adjust SCs according to QFF earn rates. For example, I had taken a few J trips to Europe with EY. Those trips typically earn 560 SCs with Velocity (rtn), but a similar trip with a OW partner would only earn about 280 QFF SCs. At least that's how I understood their process.
If you adjusted your SC earn rate along those lines, would you still earn >700 SCs per year? If not, that might have been the reason for rejection.