for what it's worth - there are contingencies for catching / preventing gfx core tunings from taking the system down when applied, but nothing can prevent failure if mclk / voltage is set to a value that the system doesn't like.If it was a problem with the stability of the undervolt then it would also black screen when applying one setting at a time and I'd have crashes in games. The fact that it only happens in Adrenalin when applying all 3 settings at the same time indicates a driver bug/glitch.
It's kind of strange: we've had these auto tuning buttons in adrenalin for some time. The Overclock VRAM button can cause an unavoidable system reset if the board doesn't like it
and yes, silicon lottery is the whole point here but also the fact that it's never static, there are safety buffers most of the time in for a reason (this is what people use to undervolt or over clock) - to let it degrade over time and still work fine with stock settings. In my case they aren't large enough to bother at all, though.