Different companies have different protocols with regard to flaring wells. It has no particular bearing on how strong a well is. Generally speaking flaring an Mcf of gas is an Mcf of gas that cannot be sold. A company that has a need to prove a productive capability (perhaps to investors or partners) might flare a well longer to impress them or to prove a sustained rate than a company that has no need to do so.
The fact that it was the same company makes the difference harder to explain but it still doesn't necessarily have any bearing to how strong the well is. It may, however, have something to do with operational issues they were having with the well. It would be highly speculative for either one of us to guess what resulted in their different treatment of the wells.
The gas company is probably burning off the gas that is not fit for sale,maybe to much water or other contaminates,when its ready for the pipe line they will stop burning it.
The longest flaring operation that I was involved in was 30 days on an onshore gas/condensate well in the middle east 15 years ago. We had drilled a horizontal well into a naturally fractured limestone (carbonate) formation. We hit a large fracture (not a bad thing) and the "bottom dropped out". While attempting to heal the fracture over a three week period with various mud formulations and cement, we lost over 160,000 oilfield barrels (42 US gallons each) of mostly fresh water and diesel fuel into the well. We had to flare to clean the well up, as our gas plant could not handle large water slugs.
We eventually got the wll clean enough for continuous production, but it was never a great well.
Good times in the oil patch...