Originally the probe did plug into the spindle. The Pc board behind the spindle was usually one of the first things to break on a new machine. LHR does not support this any longer. If you plug into the spindle and it is working.... good for you. Just know that when it no longer works you will have to go with the new Z.
If you have either old or new z and the probe is plugged into the cover BUT the options are set to spindle, your probe will crash. Make sure the options are set to "cover" on the machine.