Presumably that is a rather more restrictive list along the lines of "systems where EDSM has some info for the star but not the star class"? (no idea how that happens!)I've added a spreadsheet to the website for Unknown Stars, which are stars that EDSM doesn't have a recorded type/class for. There aren't many, only 117, but it might be an interesting expedition project at some point to go and scan these.
EDIT: Example star: https://www.edsm.net/en/system/bodies/id/15749253/name/Pyraleau+EF-W+b20-2
There must be hundreds of thousands (millions?) of systems without any star / body info at all. Basically all those submitted a long time ago plus all those where people just jonked through the system.