ASUS, MSI, and Gigabyte all ventured into non-k overclocking on their Z170 boards as well. The BIOSs that enabled it may have been labelled as betas, and I'm not sure if they're available through official channels anymore. But if Biostar gets a mention for releasing and then retracting non-k OC, I don't know why these other manufacturers aren't brought up.
Another drawback of non-k BCLK OC is that CPU core temperature can no longer be read.
Lastly, another potential topic to add is the subject of DDR4 at speeds greater than 2133 MHz. I've seen many forum questions about what CPU/mobo support for running 2400+ MHz DDR4. I'm under the impression that you need a Z170 mobo (I could be wrong), I've seen people say you need an unlocked CPU (from personal experience I know this is wrong), could be handy to add a section to clear this up.