I appreciate your explaination, but what I don't understand is what occurs in the time period from 'no light' to ignition. If the high altitude region is less than optimum, in the extended time period that the AB is attempting to light, what actually happens/changes during this time for ignition to suddenly take place?
Fuel is flowing into the exhaust stream, but either does not ignite or does not all ignite, so the A/B flame pattern is not ideal and does not produce the extra thrust it is supposed to produce.
At some point the fuel will begin igniting, and eventually the proper flame pattern will be established, and the designed thrust will be produced.