I think that logic has a couple of holes.
First, I do not agree that other Al Qaeda leaders would know if he had died in an air strike. They might eventually have figured it out, but they would not necessarily know when it happened. If he was in a remote region, he might not have been with Zawahiri for instance. It could have taken some time for them to realize he was even missing.
Second, the benefit of martyrdom might very well be outweighed if Bin Laden had died at the hands of the Great Satan...
Regardless - They still would have known at some point - In failing to honor his passing would be seen as a great insult. Furthermore AQ is not set-up as an organization of allegiance to just anyone - If UBL had passed (without some type of farewell orders via audio/video) it is very likely you'd see infighting of sorts within AQ elements. This has not been the case to date.
Second, the benefit of martyrdom might very well be outweighed if Bin Laden had died at the hands of the Great Satan...
Again, it is much easier to spin the truth then to hide a lie -
AQ could easily spin the truth of UBL death as a victory of sorts.....that he had died of natural causes...."Our great commander was kept hidden and protected by the hand of Allah and passed peacefully....All the while the infidel American's were futile in their attempts to kill him. The infidels filled our skys with aircraft and our lands with soldiers and yet they were still shown to be no match for Allah who while protecting our Sheik stains our sacred ground with their own blood daily...And so now we announce that our Sheik has passed....He lived as long as Allah decreed, for no other way is possible....no matter of the infidels futile efforts."