I'v seen this mentioned on other forums recently. The fact that a ref is being assessed during a game seems to affect the decisions he gives- it seems to resort to reffing by the book and letting nothing go.
Today's game v Killingworth saw the ref being assessed, actually by two assessors. I guess its only human nature that the ref will constantly be aware he's being watched- must be like doing your driving test.
In my opinion. this particular ref had a far better game earlier this season when no assessor was present- or is that just a co-incidence?