Jeff - WRONG is a big word - more likely that it is unclear - I tend to agree with your interpretation
Everybody has the rules to hand
http://www.srrs.org.uk/EN/store/PDFS/Daily Mail RBS REGS 2010.11 FINAL.pdf
1.2 All matches must be played in accordance with the iRB Laws and Regulations, Rugby Football Union Rules and Regulations and ERFSU Rules and Regulations, with particular reference to Under 19 variations specific to each Age Grade.
So the law is not varied for this competition, the point below is just guidance and competition rules and somewhat ambiguous
, how unusual in rugby law! The Refs responsibilities (and therefore risks) are surely fine as long as he act within the law
6.10 Should a fifty point differential occur at any time during a match, then the Referee will end the match and the result at that time will stand, unless both teams are in agreement to continue.
the 'unless' surely means that if both teams agree to continue the result at that time does not stand, scoring continues, and the match can end at any time provided the differential remains, and the teams agree!