I would be surprised if they didn't manually accept them, but it is a bit strange they don't mention it on their website.

I'd be very surprised if any of these companies they list are willing to give project files for manufacture. I assume they do this because smaller companies and hobbyist see it as more convienient, and to CircuitHub it means less mistakes / time dealing with the customer when they generate their own outputs.

It is on their website that gerbers are not accepted. It’s their policy unfortunately

I didn’t design the PCB so all I have are gerbers and BOMs (as CSV)