Moreover it seems debatable whether switching projects with the APIs is something that should be allowed on a project basis. If project A allows it but project B doesn't then there's no way to switch back to project A. So maybe it's better to have this API configuration option for the JAS backend project only. Subsequently the project API calls should be inline with how the backend handles multi project sessions. 

Long story short if a project API call is done it should annex the current session and leave it in tact (i.e. don't overwrite). If the selected project doesn't have a session it will create it and if it does already exist it will reuse it.