With light-locker running, you can switch back to VT7, but it will block your access to the running session there and automatically redirect you to VT8.
So yeah, going to a new VT is expected and part of the plan. If you don't have light-locker running, then of course this will be a problem, because your session will be unlocked and unprotected (as with any other screenlocker, it only works when installed ;)).
With light-locker running, you can switch back to VT7, but it will block your access to the running session there and automatically redirect you to VT8.
So yeah, going to a new VT is expected and part of the plan. If you don't have light-locker running, then of course this will be a problem, because your session will be unlocked and unprotected (as with any other screenlocker, it only works when installed ;)).