No it doesnt. Because you could have made the trade and protected Kerfoot with the 7-3-1 route and let them take one of Holl or Dermott who are both arent playing well and are currently being shopped 10 games into the season. It just proves how stupid it was to make the trade and expose the player to "protect" Kerfott and Holl only to shop Holl a few months later after being a healthy scratch.
Protect Matthews, Marner, Tavares, Nylander, Kerfoot, McCann, a 7th forward, Rielly, Muzzin, Brodie and Campbell,
Expose Holl and Dermott.
Justin Holl was a regular top 4, right shot, defenceman with size playing successfully on our shutdown pairing for $2m with term remaining. Last year was the first in many years that the Leafs D wasn't a problem / area of concern.
Losing Justin Holl was simply not a consideration / option for the Leafs at the time.
You can disagree with whether the Leafs
should have taken the approach of committing to Holl.... but once they made / accept that decision, the McCann-Hallander swap was actually quite shrewd.
Kerfoot may have been a favourite target many fans this summer, but the reality is, Toronto was coming off a playoff loss where their #2C went down 10 minutes into the series. Kerfoot was a big reason why Toronto was able to go up 3-1 in the series, and why they were 2 OT losses away from moving on. Obviously the Leafs wanted to go heavy shut-down with their 3rd line in David Kampf, but they likely recognized the importance of having a "backup" #2 centre in the lineup.
If the Leafs had asked Seattle to "take Hallander and a 7th, but leave Kerfoot alone" -- they would have likely been hung up on. By trading for McCann, they were able to accomplish exactly that.
It's a galaxy brain move, but they looked at the situation, realized that there's going to be a lot of quality left-shot, 2-way defencemen available, so Dermott wasn't likely to get picked. They weren't prepared to lose Holl, they didn't want to lose Kerfoot so they went out and made sure that the Kraken have another viable option, and if they still decide on Kerfoot, well then the Leafs have an instant-replacement in McCann.
If Toronto was intent on keeping both McCann & Kerfoot, then yes, an argument could have been made that they should have gone 7-3-1; but the reality is, they couldn't afford to keep both. To put it another way, the difference between Kerfoot & McCann was likely viewed as negligible compared to the expected difference that losing Holl was going to create.