bin/ssh-connect is a wrapper around ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null. This combination of options means that the following warning will always be written to stderr:
ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -T dweller@secure.phabricator.com
Warning: Permanently added 'secure.phabricator.com,52.9.197.161' (RSA) to the list of known hosts. phabricator-ssh-exec: Welcome to Phabricator. You are logged in as joshuaspence. You haven't specified a command to run. This means you're requesting an interactive shell, but Phabricator does not provide an interactive shell over SSH. Usually, you should run a command like `git clone` or `hg push` rather than connecting directly with SSH. Supported commands are: conduit, git-lfs-authenticate, git-receive-pack, git-upload-pack, hg, svnserve.