Yes currently installation order matters when their are version dependencies. If you have added a package A independently (the latest version) to an environment, and later try to add package B which depends on a different version of package A, then currently the pkg manager does not auto-regrade package A. Instead the pkg manager throws a warning that the version of A you have already is not compatible with the version of B you’re trying to install.
It’s different when you add package A to an environment with B, because A does not depend on a version of B. So in this case the pkg manager gives you a version of A which is compatible with B’s Project.toml.