On BF52x and BF54x processors, the FIFO size for EP5-EP7 is 1024 bytes. Hence if the application demands to disable double buffering, the MaxPacketSize has to be set for >512 bytes.
As per the USB spec, the MaxPacketSize is 512 bytes. Setting a value >512 bytes in the RXMAXP/TXMAXP registers wouldn't actually violate the spec. In Device mode, the host knows the endpoint descriptor value of 512 bytes was sent during enumeration. In host mode, the device doesn't need to know what you program in the RXMAXP/TXMAXP registers. Thus, setting a value >512 bytes (for EP5-EP7) in RXMAXP/TXMAXP registers disbales double buffering.