Yes, it benefited (won) by the others being down. The article refers to placement, not absolute sales numbers.
Also your original argument was that Switch was affecting PS4/XBO and nothing in that article indicates that, it mentions how they are down due to age and upcoming successors, not because of Switch.
Well, the part you saying the article refers just to placement but not absolute numbers is something you made up.
The article in fact is saying both things, that PS4/XBO are slowing down because old age (no mention of Switch eating sales), and that the lack of competition is benefiting Switch (the article specifically says Switch received a "potential boost in sales" just after saying it was because "a reflection (causality) of the competition feeling a bit long-in-the-tooth".
In conclusion, the article is saying PS4+XBO were not affected by Switch itself but by themselves (because they're old), but Switch was indeed benefited (boosting sales) because of PS4/XBO going down this year.