In general, I agree I would have started Campbell for a game, probably the Pittsburgh game in which the Leafs won 4-0. However, he started Andersen and they had their most complete game of the year.
One of the issues I raised about the trading of McElhinney was that not only had he done a good job, but that Andersen could feel comfortable knowing he was the #1, due to Curtis age. Goaltending is a mental position, where confidence is a huge factor. Keefe is expressing this confidence, and we have to assume it's genuine.
I think Keefe has taken this approach and put to rest any doubt that Andersen is his guy. He has earned it, even if he's had an off year by his standards (though it's not over yet, he could finish like a lion). The thinking, I suppose, is to let Freddie know, "just focus on your job, you're the guy".
My personal opinion is that at this time of the year with so much at stake, you go with the hot hand, no matter what. Even with the big difference in salary and stature. Ultimately, with Freddie winning the last three, no matter how, he should stay with him until it's time for a break.