Jailkit only forces a particular user to remain within a specified directory.
Each of the AJXP repositories created uses the shell account respective to the current user- so there can't really be any permissions error. In my case the user logged in must have write access.
The shell authentication happens in the background, as does the creation of repositories. The user doesn't even have to know that the account exists (if it is permissible to hide it from them in ISPC3). Actually I might block SSH from the hardware firewall and allow it only from the AJXP server.
You can see that the session credential isn't enough for access to all the user's repositories across multiple servers.