Your assumption is that the teachers (lefty lazy deceitful b'stards) all got together, rubbing their hands with glee, saying, "We're gonna really stick it to the man this year!". Then thought of a number, doubled it and added 10% for luck.
It makes much better forum fodder than the atualite, that's exam boards saying, "This is the methodology you must use for this year's centre-based grading. We require this evidence."
But hey, old Filly floated his turd in the pool and the acolytes swam over for a sniff...