[ledauphin]

this is likely in reference to the fact that dicts have maintained insertion order since Python ~3.6 as property of the language. Mathematically there's no defined order to a set, and a dict is really just a set in disguise, but it's very convenient for determinism to "add" this invariant to the language.

[zahlman]

Sets use a different implementation intentionally (i.e. they are not "a dict without values") exactly because it's expected that they have different use cases (e.g. union/intersection operations).

[jonathaneunice]

Debugging is a completely different and better animal when collections have a predictable ordering. Else, every dict needs ordering before printing, studying, or comparing. Needlessly onerous, even if philosophically justifiable.