Indeed, and I pointed that out as interesting factorThe quote you posted from the pre-trial hearing contains several references from both sides to whether the people concerned did, or did not adhere to the laws of rugby. They are using that to bolster their arguments.
But this case isn't one where they agree on the facts, but have different opinions on the meanings of the laws of the game
This is one where they agree on the laws of the game but disagree on the facts. So having an elite referee there won't help.
Legally, I am not sure it really matters anyway
The defence will argue that
'It was a rugby injury, arising through the risks inherent in playing the game.'
'The claimant, by participating in the match impliedly consented to the risk of injury, which has resulted in her injury
As an example being tackled late is clearly again the laws of rugby .. but is also clearly a foreseeable risk you "consent to" when deciding to play .
Statements from witnesses will be important, as to what actually happened but I don't think the referees witness statement will be any more or less valuable than a player, per se