Here is my 2 cents:
There are 2 stages: Flight preparation and Flight procedure
If you have taken not less the minimum required for dispatch you are covered. This is the theoretical, the legal part at Flight preparation.
Now due to unforeseen circumstances at one point you have an actual fuel quantity less than planned. Now you are faced to the reality so you do not care about the Flight preparation anymore. Now it is about Flight procedure. What Flight procedure says is about MINIMUM FUEL and LOW FUEL.
LOW FUEL is simple: when the calculated usable fuel predicted to be available upon landing at the nearest aerodrome where a safe landing can be made is less than the planned final reserve fuel. (Planned final reserve # final reserve but this is another story, just let’s say less than 30 mn for jet)
MINIMUM FUEL: all planned aerodrome options have been reduced to a specific aerodrome of intended landing and any change to the existing clearance may result in landing with less than the planned final reserve fuel.
Both statements DO NOT mention that the “specific aerodrome of intended landing” must be your alternate A. It can be also your original destination, here B:
After assessment you have decided to land at your destination B, meaning you are not in Minimum fuel at all because B is now your “specific aerodrome of intended landing” and after the go around and a second approach you still have maybe 1h25mn which is far more than the final reserve. BUT If you have decided to divert to the alternate A then you are in Minimum fuel or even Low fuel.
For me, saying that you have to divert straight to the alternate (whatever the situation) whenever your planned landing fuel is less than alt + final reserve is just absurd (sorry for the word)