Be nice if people would test their theories before posting.
The hour phase hypothesis is even less likely to be implemented in the game than the moon phase.
Besides while breaking carp into Fire crystals, I just got Ice at 4:12, stabilized next round and Lightning at 4:20. 2 synths later, Ice again at 5:24. And Lightning at 6:15.
So "hour" doesn't make a difference.
Why Lightning? Because it is the elemental of the crystal used for the recipe. I get this element most often.
Why Ice? No clue. Maybe because it's the element totally unrelated to lightning. I get this element a bit less often than lightning.
I do get the other elements once in a while.
My elemental affinity is 80 for all except for Lightning/Wind at 92.