> AC759 reached a minimum altitude of 59 feet (18 m) above ground level, comparable to the 55 ft 10 in (17.02 m) tail height of a Boeing 787-9, two of which were on Taxiway C
I think what happened is that it reached that minimum, but not while directly above the tail of a 787. By the time it was directly above one of the 787s, it had gained another 9 feet.
But I could be wrong in my interpretation...