More than just that, procgen as a whole requires an entirely different level of vigilance to avoid nondeterminism creeping in if the game requires it to be reproducible. None of the inputs to the procgen algorithm can be allowed to even so much as brush up against code you aren't actively exerting complete control over, and care is required to avoid inadvertently encountering any platform specific hardware quirks.

It can also be a good idea to split the RNG into a tree for different areas (i.e. seed multiple RNGs from the main one), so that adjusting the generation for one aspect doesn't shift around everything else in a seed (especially in something like Minecraft where different parts of the world might be generated on different versions of the game).

(Note this is roughly what slay the spire did, but if they were to use a 'master' RNG output as the source of these sub-seeds then these correlations would also not be a problem. With a custom implementation they could save the RNG state directly as opposed to hacking around calling the RNG X times on loading a save)

What's burned me before is iterating over hash maps. B-tree maps (or hash maps that are guaranteed to iterate in insertion order, or any fixed order) are your friend.