It is true
Locked myself several civ planes with optics during training. Once the radar was on accidentially, but I switched off. Without countermeasures on our (TELAR) radar you see something similar (cone/sector), if you are under radar lock. Actually the optics and image processing capabilities were so good, that you can lock to a person also. Or a rabbit. Can not disclose range for that, classifed info. This was not BUK.