Many other potential variables as well. When experiencing this event, how long does it take your heart rate to reach a point it can be identified as worthy of triggering the switch? Is the laptop still in range of your smart watch at that point? Then there's the reliability of the wireless connection and the watches ability to accurately read your heart rate (make sure it's seated correctly).
If this is a situation you're actually concerned about, the approach in the article seems simpler and more foolproof.
I assume you would want the computer to be locked if the watch signal dropped and being concerned enough to desire the feature in question. I'm doubtful one's heart rate isn't increasing in an event of theft and where it wouldn't lock a person out in time before for a person significantly uses the device. There are multiple variables but I can also see the wired approach being futile in situations where a person is pinned down by multiple people.
If this is a situation you're actually concerned about, the approach in the article seems simpler and more foolproof.