proto3 messsage fields allow for detecting set vs. not set; other field types (repeated, map, int32, string, bool, enum, etc.) have this "default value if not set" issue. The canonical way of handling this is to use wrapper messages (because one can detect if the wrapper is not set), and there are "well-known" canned messages/protos one can import and use without writing their own: https://protobuf.dev/reference/protobuf/google.protobuf/
Whether the codegen/libraries for a particular language provides a more idiomatic binding for these well-known wrappers is up to the implementation - for example, golang libraries have conveniences added for well known libraries: https://pkg.go.dev/google.golang.org/protobuf/types/known. Rust libraries may have the same; I'm not as familiar with the ecosystem there.
Whether the codegen/libraries for a particular language provides a more idiomatic binding for these well-known wrappers is up to the implementation - for example, golang libraries have conveniences added for well known libraries: https://pkg.go.dev/google.golang.org/protobuf/types/known. Rust libraries may have the same; I'm not as familiar with the ecosystem there.