The script you posted is only portable in theory and not in practice. Executing it while using a non-POSIX shell like Elvish (even without having it as a default shell) makes it immediately fail.
Meanwhile, `#!/usr/bin/env` is completely portable in the practical sense. Even systems with non-standard paths like NixOS, Termux and GoboLinux patch in support for it specifically.
Meanwhile, `#!/usr/bin/env` is completely portable in the practical sense. Even systems with non-standard paths like NixOS, Termux and GoboLinux patch in support for it specifically.