It's a TeX distro that only supports the XeTeX engine. A far cry from "modern", as XeTeX is an abandoned engine that always had quirky compatibility problems.
And it's not "self-contained" either if it downloads packages from the Internet.
XeTeX allows me to use the system’s Truetype/Opentype fonts and Unicode without any of pdfTeX/Metafont voodoo necessary in previous times, and it did this flawlessly for more than ten years for me. LuaTeX took ages to finally get a 1.0 version, so there was at least a period of 8 to 10 years where XeTeX was simply the best and only solution.
And it's not "self-contained" either if it downloads packages from the Internet.