They are different:

    "0": ">=0.0.0, <1.0.0"
    "0.9": ">=0.9.0, <1.0.0"
    "0.9.3": ">=0.9.3, <1.0.0"

The reason for this is that unless otherwise specified, the ^ operator is used, so "0.9" is actually "^0.9", which then gets translated into the kind of range specifier I showed above.

There are other operators you can use, these are the common ones:

    (default) ^ Semver compatible, as described above
    >= Inclusive lower bound only
    < Exclusive upper bound only
    = Exact bound

For this reason, if you are writing a library, you should in almost all cases stick to regular semver-compatible dependency specifications.

For binaries, it is more common to want exact control over versions and you don't have downstream consumers for whom your exact constraints would be a nightmare.