Hmm I don't think you can technically have a flush five that's not counted as a flush, since right now you always need all five cards to be the same rank and suit for it to be a flush five, and so I can't think of a way that wouldn't be counted as a flush, even if you had no plastic bricks.
My code defines a straight flush as more than just both having a straight and a flush. There must be the consecutive cards of the same suit. That is, unless you have four snakes and four plastic bricks.
So for example if you have two plastic bricks and two snakes, you need three cards to make a straight, three to make a flush, and three to make a straight flush. With that in mind, consider the following hand:
3h 4h 5s 9h
This hand contains a straight, and a flush, but not a straight flush. If the 5s were instead a 5h, it would be a straight flush.
Today I implemented a system that *should* help with this confusion a bit. The tooltips that come up when hovering over a hand will update when baubles are purchased that change how the hand is defined. I'll upload the new build tonight, as usual.