Are USB 3 ports really completely compatible with USB 2 devices?

Are USB 3 ports completely compatible with USB 2 devices?

For flash drives and external hard drives this seems to be true with my ASROCK z790 Lightning motherboard with 32GB of memory and i5-12600K cpu.

The USB 3 ports do not seem to work properly with USB 2 devices like SDR (software defined radio), (buffer overruns) or my ICOM IC-7100 Amateur (Ham) transceiver running Winlink applications (connection recognized in device manager as COM 3 and COM 4 but radio can not be accessed by Winlink or VARA applications).
If I plug these devices into true USB 2 ports they work perfectly.
Just trying to understand how truly backward compatible USB 3 ports are with USB 2 devices or perhaps there are some driver or configuration changes needed to be made.
The ICOM IC-7100 radio USB interface uses Silicon Labs CP210x USB to UART Bridge drivers.
I've seen this happen with Windows 11 and Windows 10 computers.
Thanks,
Steve

They should be backwards compatible, but it may be a driver thing with your devices.

I use the Silicon Labs CP210x USB to UART Bridge extensively and it works fine in USB3 ports for me.

BIOS :

Legacy USB Support: [Enabled]
XHCI Hand-off: [Enabled]