Indeed. It is not clear how it happened, of course, whether the MD was backed onto the wing-tip, whether t'other was 'swung' into the tail or even if the near a/c was taxying off with a turn as the other was pushed. Someone knows (and someone 'pays')! Judging by the quote, "Delta spokeswoman Chris Kelly Singley" is not one of those
Some push-backs use 'wing walkers' who check tip clearance (but not 'tail walkers').