Yep. We considered building an M.2 2230 NVMe USB-C adapter, but it was more efficient to just use a USB-C NAND Flash controller that interfaces the same types of flash that NVMe SSDs do. One less layer of translation.
Plenty of USB-C SSDs on the market are actually M.2 in a trenchcoat, e.g. the nice looking black and orange SanDisk: https://www.reddit.com/r/hardware/comments/9631os/sandisk_ex...