You can definitely pass a PSBT file from any airgapped device but remember some of these devices aren't a panacea.

Some people have had trouble sending large amount of inputs in one TX (140+) with some devices. The HWW couldn't absorb the PSBT generated to sign - legit failure.

HWWs can also make your Bitcoins less safe by using their Random Number Generators & trusting that your device is legit & not tampered with.

I do understand the use of HWWs for signing, but people store their seeds on these HWWs which are only protected with a pin code!!

This is the point you've missed^