In a letter sent to the three clubs, NRL chief executive Todd Greenberg said he was not calling into question the integrity or professionalism of any of the club's medical staff.
McGregor was reluctant to be brought into the discussion when asked yesterday, but made a point to stand by his staff and their decisions.
"Certainly the welfare of our players is the most important thing to us," McGregor said.
"And the integrity of my staff should never be questioned."
The round-three breaches are the only incidents to be reported this season, with Greenberg stating on Thursday he was happy with the way the competition had since treated concussions.
St George Illawarra's fine relates to their decision to keep fullback Josh Dugan on the field after he was struck by teammate Russell Packer's elbow in their 16-10 win over Cronulla.
McGregor said at the time he was told Dugan's reason for being slower to rise was a jaw injury, and he did not believe there was any concussion-related problem.
The Dragons claim the sideline television monitor was malfunctioning at the time, denying club doctor Tom Carrigan a chance to review the footage.
"If you look at the situation there was no vision for our doctor to be looked at," McGregor said yesterday.
McGregor's frustration echoed the Dragons initial statement on Thursday, which said the club was disappointed with the process and the NRL's considerations.