You don't necessarily need to check the code. A statistical study with a large enough sample of data would suffice. I think that's what someone did, probably on the French server. But I'm too lazy to dig out that thread or search again the exact source where I read about it.
On a personal level, there are too many coincidences. The green pearl (which I had never found before) is an example, and of course an example is nowhere near a proof. But many similar situations are a hint. Too often I keep finding the same items during the same game, like 4 (or was it 5)

. Too often an item which appears in the very first levels will appear again immediately. And lastly, the distribution of the collected rare items is not random at all, which is probably the major hint about some modifiers being implemented.
That said, I keep dying in Hell 8, usually too often even in the previous levels.
That will be a long way to go for the pyramid.
