It seems to me a lot of Android phone companies don't implement wifi roaming well.
I am pretty sure Android can support 802.11 k / v / r. But take my case for example - even with a new Xiaomi flagship phone, I had to tweak its wifi WCNSS driver to make it work, and only some of the time. And if I don't root my phone it wouldn't even have been possible to make those tweaks.
(can share with you what I have done, but I think there are different modification for different brands of phone / wifi chip used. PM me if interested !)
I am still encountering some issues, check out Strange problem with 802.11k and 802.11v that I have just posted.
But so far what I can conclude is that at least for my Android phone, I don't even need Dawn to be running. Like the iDevices, it makes its own decisions on which AP has the best connection quality and which one to switch to. But unlike the iPhone, it needs 802.11k/v to be up and running (this is the case for my phone anyway) to feed info to it for making the decisions.