More than likely what they meant was that he wasn't qualified to be teaching in the STRIKE phase of T-45 training which would include the low level training - - - - not that he wasn't qualified to teach in the airplane.
Edit: Now after reading the article (yes I answered before reading the article :roll eyes
, it does say:
Bynum noted that the flight’s purpose was low altitude awareness training and they were initially on an approved training route, but that the instructor, Ruth, deviated from proper procedure and also encouraged Burch to do the same.
My guess was that he wasn't STRIKE qualified and doing low levels, but this last sentence seems to say otherwise; if he was truly getting low level 'Xs' per the flight schedule, unless it was a oversight that he had been scheduled for this type of training and maybe had not completed the STRIKE IUT syllabus, therefore not being qualified yet.