"List" has no "Except"

I happened to notice that List in Unityscript, has no “Except”

{ ie, List<T> Class (System.Collections.Generic) | Microsoft Learn
Enumerable.Except Method (System.Linq) | Microsoft Learn

for example
abde = abcde.Except(cfgh); }

No problem, but what’s the 'explanation" for that, system experts ?

Like, does Unity use an “older version” of “the well-known compact version with documentation here” … or what’s the deal?

(In fact, would these differences be listed anywhere??) Thanks !

You’ve got the Linq one. As for why it isn’t in the standard List, no idea !