Possibly a bug here?

Feedback and Suggestions
#1

Since I have no inside into the code, it is hard to tell, but I observed a statistical deviation that is beyond any reason when it comes to replacing starting cards.

So I made a deck with only 1 copy per card, and played it extensively. The amount of times I received exactly the same card I selected to replace was insane. It should be 1/30 but it was nowhere near it.

Maybe there is a bug or just subpar implementation of the random seed or something like that?
Or maybe I just got a really unlucky streak for a Long period of time? Just wanted to bring this up for discussion.

#2

I tested something very similar here: Mulligan improvement
However, that’s only testing replacing all 3 cards.

I did this because I also felt something was wrong, but in that case it turns out it was probably just confirmation bias (i.e. my brain was probably just forgetting the “successful” mulligans but remembering the “failures”).