asrock z790 m.2 weirdness?

Hi All,am i being an idiot? i bought the above mobo and installed a (gen4) samsung 990pro into nvme slot M2_1 (gen4) yet when i look at samsung magician is says its running at gen 3, i moved the nvme out of curiosity to the M2_4 but it still gives the same result any ideas? Cpu i5...