They are just taking the average ratings. Among US advocates for electoral reform this is called Range Voting
. The only new thing (though even this is debatable since I don't know everything) is that the voting scale goes not from zero to something positive or is symmetric with positive and negative, but it goes zero to very negative. From a mathematical point of view, this is completely irrelevant. With strategic voters it works out the same (they will only use the most extreme ratings). But it might make a psychological difference.
You could do much, much worse than using average ratings. But this text appears very superficial and misleading. First of, outside of the writings of these authors the word consensus means something else. Almost any voting method in use prevents that an option A wins whenever there is an option B that Pareto-dominates
A, that is B is preferred by at least one person while nobody prefers option A to B. In that sense, consensus methods are used everywhere. But saying you "use consensus" refers to the more restrictive idea (which doesn't scale well) that literally nobody in the group is against the decision.
And second, the "analysis" of strategic voting is hilarious. Some little kids tried to be strategic and it didn't work out for them this one time, so strategy doesn't matter… SERIOUSLY?