DoubleCheck – Your suggested solution is not possible. Mojang did not start Minecraft with source control (or else there would be no lost versions) & whatever source code they may have, it would not make sense to patch the hundreds of versions of Minecraft (which would change them to NOT be those versions by the way...) when they could instead just implement a single redirect.
I know that those old versions are "unsupported" but it would be really easy to implement a redirect. Some people really like these old versions.
DoubleCheck – Your suggested solution is not possible. Mojang did not start Minecraft with source control (or else there would be no lost versions) & whatever source code they may have, it would not make sense to patch the hundreds of versions of Minecraft (which would change them to NOT be those versions by the way...) when they could instead just implement a single redirect.