I think what he's trying to say is not that nothing is probably fair, but nothing is 100% fair and random. A formula will always be restricted by parameters.
I know what he tried to say, I'm just being a jerk about it, grammar police, whatever. 
But when you say "restricted by parameters", ... 128, 256, or 512 bit output... Not something to worry about from a practical point of view. You can argue about it academically all day, won't really matter as it's essentially unpredictable and random for all intents and purposes except analyzing it. They are deterministic.
To predict a block hash, or any digit of the hash, you would need ... to actually mine.