Here is the eligibility rule. Not sure it sheds much light
33.2 A player shall not be eligible to play
in a Finals Series fixture unless:
(a) The player has played with the Club a
minimum of four rounds during the Minor
Premiership series; or
(b) The player has been on
representative duties during the current
season and has played a minimum of two
minor premiership matches in the current
season at the same Club in which he is
seeking eligibility, or has been a registered
player with the club (according to MRA)
without break for the previous two years.
(c) Players playing at an Australian Super
Rugby Franchise that dictates the player
must play in the local competition may
lodge an eligibility appeal.
33.3 A player shall not be eligible to play
in a Finals Series fixture in any grade
lower than the grade in which he has
played the majority of his last seven
matches in the minor premiership.
33.4 If a player does not qualify for a
particular grade under rule 33.3,
dispensation will be granted if the player
has played 60% of his season in the grade
in which he wishes to play. If the player
has been on representative duties as
described in 33.2, he shall be eligible for
Shute Shield, 2nd Grade or 1
st Grade Colts
only, subject to Colts eligibility.