It turns out that Blizzard have made a misstep while deploying the Overwatch League app earlier this week, as the developer accidentally enabled access to expanded Overwatch stats, much to the delight of stats lovers. It didn't last though.
Quickly after discovering their mistake, Blizzard remedied it. Overwatch League's head honcho Nate Nanzer took to reddit to address the issue, claiming that even though Blizzard and OWL appreciate the "enthusiastic response" by the fans, "that content was not intended for public consumption at this time."
The Overwatch League stats API is still up mind you, only not with the expanded stats, which is still a big deal, not least considering how long the community waited on the Blizz to deliver the feature in the first place.
However, the entire ordeal invariably ruined the surprise, since it teased a lot more Overwatch stats than we ended up getting. One reddit user dug up the full list of stats available in the API's backend, including critical hits, critical accuracy, shots hit, stats per minute of gameplay, etc.
As you'd expect, fans weren't exactly ecstatic over the backpedalling either, especially those who've already started doing in-depth analyses with some of the more esoteric stats. Yeah, of course they're going to start with Widow Maker, with reddit user Cheraws compiling a pretty nice overview which you can see here.
At the moment, Overwatch's stats API gives you access to seven stats - deaths, eliminations, final blows, healing, damage, ultimates and time played. It can still be a useful tool, with fan implementations ranging from crude, to not so crude.
One thing is clear though - Blizzard don't plan on stopping with the Overwatch League, since detailed stats usually bring about them a new age of performance analysis and, in turn, performance. In fact, you'll find quite a few statistics savvy redditors on the links above, who're looking forward to analyses of support pairs and their efficiency per match.
Unfortunately, advanced performance statistics commonly bring in betting as well, something of which I'm unsure when it comes to Overwatch, at least at this fledgling stage.