Man, that's weird... It's a seriously small sample size, but his numbers batting leadoff are GREAT, and in every other position in the lineup they're mostly awful (except batting 8th where they're about average).
I do think he's better suited to leadoff than Semien (I'm honestly not sure why Semien is the leadoff hitter while Springer is out...)
Career-wise, his best numbers come (in order) 8th, 7th, 1st, 2nd (wRC+ if 176, 130, 128, 121). He's apparently just bad when not at the top or bottom of the order. I haven't really looked at this particular split for anyone else, but that seems like a wide spread.
Of course, MOST of his career at bats are 1st or 2nd, and we're only dealing with a bit over a season's worth of total games, so it's still probably too small a sample size to draw any meaningful conclusions from... Interestingly, Cavan has never batted 9th in the majors.