To go further, semver provides semantics and an ordering but it says nothing about version requirement syntax. The caret operator to describe a range of versions is not part of the spec. It was introduced by initial semver-aware package managers such as npm or gem. Cargo decided to default to the caret operator, but it's still the caret operator.

In practice, there's no real issue with using the first non-zero component to define the group of API-compatible releases and most package managers agree on the semantics.