I think the biggest risks in this game are:
1) we don't know which 2 cards have been left out of the deck (since they only use 50 cards instead of 52, it's possible that if only 3 copies of a card have been played, the 4th one was cut from the deck)
2) like this chapter suggests, up until now only the optimal hands have been considered for each number based on the remaining cards in the deck but the numbers that Usogui and Lalo can play were predetermined, which leads me to believe either the hands themselves were predetermined as well, or as has been suggested others are making hands from the remaining cards in the deck. I haven't tested this with a deck of cards myself, but I think the combination of 10 numbers that they together have would only allow for a very narrow number of hand variations. could be wrong though. my point being that not every hand would be 'optimal' for its number value since you don't just have to make the cards add up, but also stay within the limits of a 50 card deck