> Then, the housing is 1mm past the USB-C connector.
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.
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.