What I am suggesting is that perhaps the interpretation isn't as clear cut as you might think. The number of different interpretations in this forum supports this.
I still believe there is a high likelihood that the rule was written (poorly) with planning requirements in mind.
This is NOT an attempt to 'find ways around the law', it is an attempt to think about it in a practical manner to understand what the lawmakers are aiming to achieve.
Pilots might not be getting the forecast once within sight of the field (but might overhear it being broadcast on centre), but whether they have heard it or not is irrelevant, under your interpretation of the rules, is it not? So the guy 30 miles out on a visual approach is now breaching the rules because an amended TAF has been issued?
What is wrong with a pilot using his judgement based on ALL information at hand, which includes the METAR, and a first hand assessment of the risk associated with the TAF?
One other point (not claiming its conclusive) is the CAR definition of an alternate: "alternate aerodrome means an aerodrome specified in the flight plan".