I think what happened here is that he wound the quill so far back that now it won't go forward again. This then results in a situation where none of the morse tapered centres will hold, because the ejection pin is holding them all out. In theory this should never happen, but if it does happen quite some force will be needed to push the quill forward. If the lock-up is bad enough this can have bad consequences for the handle or the pin or thread holding the handle on the quill.
Tony: you can try and force the quill forward with a small leverage on the handle on the wheel. Since your hand wheel is solid, this won't be easy, you may have to mount the whole lot back into the tailstock and see what leverage you can apply. If you do manage to force it out, I would recommend total dismantling and checking for damage.