No idea. There's an app that's supposed to test for doze and it says "hw sensors: ok" (or similar) but "config: off". Like it's configurable somewhere but wasn't enabled by Xiaomi.
My guess is that Xiaomi already has a similar feature (perhaps less sophisticated) called "Autostart". Most app aren't allowed by default to wake up in the background and kill your battery. Only some (e.g., whatsapp) are whitelisted and, of course, you may whitelist additional apps yourself.
Overall, I'm happy with the battery usage of my Mi3. I prefer the Xiaomi Apple-like UI over Google's standard -- but that may be just a habit...