Jay,
Are we not saying pretty much the same thing.....except I put a hard limit on the fuel limit....where the JAR's, Jim, You, and others state it is an Emergency, requires a Mayday Call, and an EXPEDITIOUS Landing.
I just forego all that formality and legalese and declare it to be a mandatory land absolutely as quick as possible at the nearest suitable landing spot.
When One begins to use the "Reserve" fuel....that is your notice of a pending fuel emergency.....not after you go through your "Reserve" and then on into your Minimum In-Flight Fuel level.
If we can wait until entering the Minimum In-Flight Fuel level to declare an Emergency OR make a precautionary landing then why have the ordinary everyday Reserve Fuel requirement? Upon beginning to use the standard "Reserve Fuel" is when the Radio calls should start and the Pilot making the decision where and when to land....with the dead line being hitting the Minimum In-Flight Fuel Level.
When I managed an Operation I always told the Pilots....if you need a Fuel Bowser sent to you....then no problem or repercussions beyond asking them to explain how it was they could not get to a fuel point. I also reminded them that landing with less than the Minimum In-Flight Fuel Quantity was Grounds for Dismissal. The cost of sending Fuel to a Pilot was far less than replacing the Aircraft and perhaps the Pilot and Passengers if they were to run out of Fuel and wind up destroying the aircraft and killing themselves and their passengers.