I think this would almost certainly fall under * as opposed to gambling.
I don't think any of the "gambling" in this game can be classified as gambling in the face of law, due to the fact that most of the reward does not have a known monetary value and can not, normally speaking, be cashed out. I am entirely unfamiliar with gambling laws, but considering even simple real lottery must have some kind of license and/or regulated by law, I rather doubt the ones in game qualify.
And considering gambling are illegal in some nation/state and are age restricted, if it was actually considered as gambling, it probably can't exist as a feature.

So no, probably can't pin anything gambling related to them. But *, that you probably can. It is clearly implied that 5/10% are possible, if it can be proven that they are, in fact, impossible, it would be *ulent. (and given there is a log of % winners, should be able to prove the latter)