any idea what the AIP reference is for that
There is no reference for that!
It is assumed we are smart enough to realise that if the weather is above Alternate Criteria, whether it be for the full period or inter/tempo, we don't need any extra fuel. It is not necessary for the AIP to state that.
The AIP section that deals with Alternate Aerodromes, Weather Conditions and INTER/TEMPO is:
ENR 1.1 - 92, start at para 8.8