It assumes that the average person aged 65 will live to 84, meaning as many will die before as after.
Is there a less allegedly ambiguous term for the "traditional" definition of average, that is, the sum of many measurements of the same characteristic, divided by the number of elements measured?
Average intelligence, for example, refers to median intelligence (equivalent to an IQ of 100). Mean intelligence, however, is likely the same as median intelligence due to its normal distribution.