The code in ActionType has the following:
else if ( value.toUpperCase().startsWith( "X" ) || value.toUpperCase().equals( "ACTIVATION-GROUP" ) )
but above this is a check for startsWith("A") to catch Actions which will always take precedence. Maybe it would be better to check for the full names first and then for the single letter option.
In the documentation it actually specifies that "XOR-GROUP" should be used, so the other option may be to just remove the "ACTIVATION-GROUP" check, however the current code means new options (such as agenda group for instance) would have to use letters that don't really make sense.