Even if Pangram was blessed by God to be 100% accurate no, your argument is a strawman. The reliability of the software has nothing to do with the principle behind "software should never make a management [legal / disciplinary / etc] decision." So no consequence from the tool, but perhaps it can be used as evidence in an academic integrity hearing. Maybe the university equivalent of probable cause. I am not knowledgeable enough to make a firm determination.

FWIW if I were a student I would definitely be using Track Changes or version control, etc etc, to make clear my work was human-written. Which sucks.