It would be easy to classify any play I wouldn't make as a mistake, but I don't play perfectly, and I think about whether differences might be better than what I usually do, or whether they are just as good, but a different style. I recommend this practice.
There is a common misconception that the big stack is supposed to spend those chips trying to knock players out. The ICM says the big stack is still only supposed to make plays which gain chips, and this can mean folding the small blind when the short stack is pot-committed to call with ATC. I gave an example of this in my video on the ICM.
The players most vulnerable to pressure from the big stack are the medium stacks, since they are in decent shape if they fold. A clear shortest stack is not so risk-averse against the big stack, which reduces the big stack's ability to bully correctly.
Ending the bubble by knocking out the short stack mainly benefits the medium stacks, relieving them of the worry that they will bubble out against the big stack. At times, the big stack would prefer to lose a few chips to the short stack to preserve the bubble. This is not a stupid play, although it is not as often correct as some players believe.
So, you really need to distinguish between times that the big stack is correctly not trying to pressure the short stack and ones where the big stack is really making mistakes.