It seems like there's something wrong or screwy with the implementation. The cards left in your deck always immediately increases by 1 when you play a card, but if you wait and redraw your hand and add up how many cards you've gained, your total deck size is never correct based on what it tells you it should be.
The probability of drawing certain cards also feels off. I have had opponents spray their chickens and spare parts like crazy and still continually draw their non-starting cards a lot, while using lots of restraint on the 1 mana cards had no discernible effect on my probability of drawing them. I tried spamming the spare parts and chickens myself in a subsequent game, and still couldn't tell a difference, and still seemed to get my non-starting cards a lot.
Drawing two copies of the same non-starting card should happen from time to time, but I haven't really seen it happen.
I think they got it working to a point where you can't prove it's not doing what it says it's doing without 1000 automated trials, so they got it through QA that way, but I suspect it's not quite right.