The port uses USB-C, but according to Mini Maker, it enables a direct PCIe connection which is faster than what you get when using Thunderbolt 4 to connect a laptop to an after-market eGPU like ...
Of course, if you've got a DIY NAS running Windows or a full-fledged Linux distro that plays nice with graphics cards, you can add an eGPU in case the NAS has Thunderbolt 3/4 or USB4 connectivity ...