GETSYS.PRG between lines 64 and 67

[Numerabilis]

https://github.com/harbour/core/blob/master/src/rtl/getsys.prg:
I wonder why these lines in getsys:

   IF Empty( GetList )
      SetPos( MaxRow() - 1, 0 )
      RETURN .F.
   ENDIF

I have a function which works with TBROWSE() and when I compile with xHarbour it works well but when I compile with Harbour it doesn´t work as expected. Sometimes the field don´t show in the correct place but in MAXROW()-1.
I think it happens after a READ. After a READ the GETLIST becomes empty, isn´t it?
Could someone tell me why those lines between 64 and 67 could be important?