You give a valid point, Kalin!
The devil is (always) in the details 
The Arm. Bde. AA Detachment was formed after Sep. 9th 1944 coup.
No German advice could be used when forming it as Bulgaria already had broken relations with and declared war on Nazi Germany.
But bearing in mind that the entire modernization of the Army(both structure- and equipment wise) since 1939/1940 was centered around German know-how, one cannot rule out the possibility of said transformation happening along some German KStN’s Bulgarian General Staff had.
I doubt the ones you mentioned were provided by the Germans, because they would have caused increased demands for supply of weapon systems Bulgaria lacked(f.e. 2.0 cm Flakvierling to name at least one) at times when the Wehrmacht needed these direly and would have given an ample excuse each time the German advisors tried to escalate on the issue they had with the 'lacklustre performance" Bulgarian Army showed in its modernization.
I see a trip to the Military Archive in Veliko Tarnovo shaping up…