For an ATCO to gain a Unit Endorsement on his/her licence requires intimate knowledge of ATC procedures and techniques. It is not necessary (nor feasible) to have an intimate knowledge of a/c performance and characteristics of many diverse a/c types, even though it is obviously desirable for ATCOs to continue to learn and broaden their knowledge in this regard by fam flights, liaison trips etc.
That's why pilots train......to gain an intimate knowledge of the performance and characteristics of their own aircraft.
Yes, an unfortunate situation, of course, but I hope someone will see what lessons there are in regards of the training this pilot received.