It's an unlikely entry point. But if it's that awful flexi-duct then they'd be straight out of it into whatever void it's in.
The cowl shown in the mouse video is probably mouse-proof, perhaps with a lip under it.
I wouldn't put mesh within a cooking extractor, it will soon fill with congealed cooking vapours and become a blocked mess.
The point of the video is a mouse running on a vertical wall, not the unrelated wall vent that the mouse doesn't even enter!
