The concept there is fascinating, but there are two BIG issues:
1) For all the work that appears to have been done writing the article itself, the data is pulled from: 10 hockey defensemen who were males aged 14–16 involved observation during an ice rink’s 2-hr open “puck-n-stick” session.
That's an incredibly underwhelming source of data for something this ambitious. You'd almost have to go out of your way to find a less adequate sample of hockey activity, than a tiny group of teenaged amateurs messing around at open hockey.
2) The tasks measured were all offensive in nature (holding the puck at the blue line, making passes, taking one-timers) which leaves the majority of the defenseman's job un-measured.
I like the level of detail that they explore to illustrate their findings, but I have serious reservations about the findings themselves. If someone does a more robust study, I'd be interested to see the results and I expect they will be quite different than what we see here.