Hello,
This may be due to the old version of the tool is using an old configuration for the processor, since as you can see there is no FlexSPI signals routed to PTE21, and it is safe to use it as ENET0_RXD.
Also, an small mistake from my side as I notice that i.MX8ULP EVK we use PTF1 for ENET0_RXD, but as said above there is no dedicated or FlexSPIx signals that can be routed to PTE21.
Best regards/Saludos,
Aldo.