I still believe other experiences can matter, AND not matter. For example, if 70% of the people said they had great luck you would assume all is well, but that also means that 30% did not.

Or, those flying from San Fran to LAX had great luck, but those flying Boise to LAX had bad luck. And of course, there is always the weather that changes everything. If the flight before yours was cancelled, your chances of getting a seat would be a negative 50% (random number, but you get the point).

As to one agent saying there were a few people ahead of you, and the next saying you were the only one - that is very possible. Those others could have been cleared right after you asked the first time.