Did you look to see if the prior reports of his death were ever written into the account? You can see all the past edits.
I could see editors arguing that those reports belonged in the entry on Osama Bin Laden more than the entry on the death of Osama Bin Laden, however. As they were not about the ACTUAL death.
Still, bias is real everywhere. I think it's pretty clear tho that the bias in Wikipedia, which is no doubt real, is crowdsourced... it's not something created by the Wikimedia staff.