This is because the shebang is #!/bin/bash which is not standards compliant and NixOS does not expose this. The compliant shebang that works on all systems is #!/usr/bin/env bash (according to the NixOS user). The impact of this is that when I do user interview calls for Datomic Browser and ask users to install Datomic Pro with mbrainz, NixOS users get errors on restore-db etc. The resolution is I have to instruct them to edit in place the Datomic shell scripts in bin/ to rewrite their shebang to the correct value.
datomic pro 1.0.7469