This isn't really true for PCIe 4 and beyond. For example, if you use a competently manufactured PCIe 3 riser in a PCIe 4 GPU configuration then VGA will fail

This isn't really true for PCIe 4 and beyond. For example, if you use a competently manufactured PCIe 3 riser in a PCIe 4 GPU configuration then VGA will fail to POST more times than it succeeds (on the order of successfully booting 1/10), if it POSTs at all. Given how expensive PCIe 4 risers are most people choose to downgrade to PCIe 3 in the firmware settings.