Interesting question...in theory the bolt only being held by the threaded part of the ball joint means it's not locked, how ever if you add a nyloc or even drill that out to 12mm and replace with standard M12 bolt and nyloc it is considered locked. You could of course try and find a castle nut and split pin it if you can drill through.
This the reason I don't weld the nuts on the under side of CP3/4 as using nylocs is one less simple fail to worry about...
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