Except that we don't even know if he's a quality platoon candidate, as evidenced by his .405 (!) BABIP against lefties, which is surely going to plummet.
What happens if that BABIP normalizes? Is he still a good platoon player? In this case, he probably is but he's not going to be nearly as good as he was in 2013.
Not to mention that right-handed platoon players are marginalized to begin with, as it's so easy for teams to negate his split advantage after 5-6 innings. Also, LHP starters are far more uncommon than their right-handed equivalents. If Valencia is going to play at all, he's going to get 30-40% of his ABs against RHP.
Platoons are great when they work but the left-handed hitter in a platoon is going to be far more valuable than the right-handed hitter in the same platoon.
His career splits still indicate a guy that could hit lefties very well. You couple that with Moustakas and you might have a nice little fit.
All they did was swap similar players with different positions. If you want to hop aboard the "Bash Dayton Moore" train, that left the Omar Infante station a few days ago. But this ain't it.