No, Arria® V GX devices do not support transceiver PMA Direct mode.
You may see the following error if you try and compile a Native PHY in PMA Direct mode on Arria V GX devices.
Error: Channel PLL Parameter 'output_clock_frequency' is set to an illegal value of 'x MHz' and PMA Direct parameter is set to 'true'. If PMA Direct is false, the value is illegal for protocol mode: '' with a device speed grade of '6_Hx', PMA WIDTH of '' and byte deserializer mode : '' and latency '' on atom