The 7450 spec sheet[0] lists 1M iops read for the U.2 connector, 735k is for the M.2. And that's a PCIe Gen4 drive. If you look at the Micron 9550 Pro[1] (Gen5) the specsheet lists 3M IOPS for the 3.2TB model.
I have a strong suspicion that difference is due to heat dissipation of different form-factors, not due to connector. But yeah, it looks like whatever AWS is using is not on par with modern drives indeed, a factor of 10 to the drive you linked is a huge difference.