I'm curious how the USB-C connectors are made to the outside of the enclosure. What I've found is that it's a bad idea to use USB extension cables; these can introduce bit errors if e.g. you copy large amounts of data (order of terabytes). It's much better to insert a USB drive directly into a carrier board, but this is not always physically possible.
It's almost standard to have the USB-C have extra wiggle-room (around 1mm or so). Then, the housing is 1mm past the USB-C connector. That's how the casings are made so that when you stick the connector in, it's flush or nearly so. I agree with USB extension cables concerns too! The error would increase depending on the quality (impedance, power, etc.)
Yes, this is often the case but sometimes the USB-C connectors are on the same side of the board where you also need to plug in some cables that you need internally (maybe even other USB devices). Thus the option of letting an USB-C port stick out on one side of the enclosure is not always available.
> I agree with USB extension cables concerns too! The error would increase depending on the quality (impedance, power, etc.)
Yes, and the user of your device (who doesn't see the internal cable) will assume that they can plug in their own cable, so you'll have two cables.