Is This Normal?

Hello everyone,
Used Oracle AC turntable I purchased few months ago came with Denon DA-401 tonearm installed. I never had an experience with Denon Tonearms...But I noticed that I can easily disconnect a tonearm from its base by simple pulling it away....If not a wire that goes inside the tonearm I would completely separate a tonearm from its base....I wonder if it is normal...I thought that in such mechanisms like a tonearms everhing should be very presice....but having tonearm sitting "freely" or "loosy" in its base there could be some not needed space for uncontrolled shaking, tilting, moving....It is just doesn't lool right to me...I would appreciate if anyone with experience with similar tonearms would clarify me a reason why tonearms would be made such way? Here are two images of the tonearm area where the disconnection happens:

This is indeed unusual. Look around the base where the upper part of the arm fits and see if there is a threaded hole or maybe two holes. Seems to me as if there is a screw missing.