In practice, we assume 0.y.z be compatible with 0.y.a, a < z or the other way round depending on which direction you're looking at. I'm not sure if this is a rust fortification of semver
This is backed by the cargo manual <https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html>:
An update is allowed if the new version number does not modify the left-most non-zero digit in the major, minor, patch grouping.
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