Sorry, but that theory seems like horseshit to me. If 1000 people watched something, and 1000 people finished it, then the completion rate is 100%, but who cares because so few people watched it. Also, maybe the author wants to take a stab at why Sense8 was cancelled then.
I'm not saying completion rate doesn't matter, but there are other variables at play. Also, by cancelling a show, they're outright having a direct impact on that completion rate - for those that haven't finished it, why bother now? For those of us that never started it, well, we sure as shit aren't going to complete it now either.
I can't see this as anything other than the 'instant gratification' of society today. If something isn't a success out of the gate for Netflix, it's at risk.