MinUI OS Subsystem is a pared down fork of JELOS used as the foundation for MinUI on the RGB30.
You can grab the latest version here.
Two reasons. The first is practical. Installing a JELOS update over MOSS, or vice versa, would break everything. JELOS has a built-in feature that prevents accidentally updating from a different distro. The name change takes advantage of this existing feature. The second is expectations. While MOSS is just JELOS under the hood, it doesn't support all the things people love about JELOS so it would be misleading to call it JELOS. My plan is to treat it like the frozen firmware of the nand-based devices MinUI supports.