Why are these operators seemingly hardcoded?

          LeftAngleEqual `with` string "<=",
          RightAngle `with` string ">",
          RightAngleEqual `with` string ">=",
          FSlashEqual `with` string "/=",

Surely the has to work with custom operators too. So why treat these operators distinctly in the lexer? Operators are just infix identifiers. The parser has to detect that there is infix application going on. Is it because they’ve just decided to not support operator overloading?