Waren9 - sorry, my scenario was badly worded.
The fuel at start is 65 tons (this includes 2 tons variable reserve).
My fuel at CP is planned at 22.8 tons (still including variable reserve).
Because the CP diversion fuel is critical, there is an EDTO fuel build-up included in the start fuel and hence in this 22.8 tons. Thus the flight plan shows the CP fuel and the diversion fuel to be 22.8 tons.
Yes, the 22.8 diversion fuel contains 5% PDA buffer and another 5% wind factor buffer, but this extra 2.3 tons buffer is supposed to be there at the CP with the fuel tanks reading 22.8 tons! If you have burned your variable reserve on the way to the CP, then you are going to have 20.8 at the CP and flame the engines out on the roll-out at the alternate.
A bit too fine for my liking.