In the KSDK, there is a GPIO_DRV_ClearPinIntFlag to clear the interrupt for a particular pin on a port.
Why is there not a equivalent function to get the interrupt status of a pin?
Like GPIO_DRV_GetPintIntFlag or something like that to you can easily test in the port wide PORTx_IRQHandler which pin was causing the interrupt.
There is already a PORT_HAL_IsPinIntPending ...
You have sort of answered your own question. The GPIO Driver is meant to only be an interface to the GPIO peripheral. So if you look at the GPIO chapter in the reference manual, you will see that none of those registers can indicate that an interrupt has occurred on that pin. That functionality is found in the PORT block. That is why you find a PORT_HAL_IsPinIntPending function but no equivalent function in the GPIO driver.
After reviewing this though, I will submit a feature request for this. At this stage in the development cycle, it definitely won't be in the 1.2 release of the SDK but may be in the next one after that.