Carry out anti-theft after 21st acceptance?

Moin people, I bought last year a Kawasaki KX 250 F where the TÜV expired. I finished it so far but now I have the problem that a “theft protection” is not registered. The Kawa has no handlebar lock, I have only retrofitted an ignition lock. I then talked with 2 TÜV examiners and both meant that e.g. a brake disc lock under 21. must be entered and this is only done by the TÜV examiner who made the 21ers at the Mopeze My question is now, is it true what the two have said or is there another possibility and how can I look who or where the 21s has been made? I only know that the Kawa got a road registration right after the purchase, so 2004 and thus also a couple times came through the TÜV