There's a reason that zuck has tape over his webcam and a 3.5mm dummy plugged into his combo headphone/mic jack
How would a 3.5mm dummy mic jack prevent software from just changing the input mic source to the built in one?
Yeah but he's also WAAAAYYYYY more likely to be targeted than any of us, I would argue.
The odds of being targeted don't matter in what we're talking about. The fact its possible is what we're talking about. High value targets like zuck being well aware of that fact, and taking steps to guard against it is just icing on the cake.