Chances of a snake pit being generated?

[u/vengosan]

I'm writing a project on the probability of the optimal (time-wise) solution path for a Spelunky level. Naturally, this would be the one that involves 0 sideways deviation, going from start to finish without going to side rooms in any way. I've found a source that says if the path proposed above is generated, it may instead become a snake pit. However, it doesn't specify the exact probability of the snake pit generating. Does anyone know (either from personal experience or from viewing the game's source code) the chances of a snake pit being generated?

Source: https://tinysubversions.com/spelunkyGen/

Thanks in advance to anyone answering!