I don’t see at as a big issue. I do see it as an indicator that he us not very familiar with how most people quote scripture references. Which could possibly be an indicator that he doesn’t spend much time with scripture study. An observation to add to your picture of the man.
That exactly sums it up. To me the telling thing about Trump was not that incorrectly referenced Second Corinthians, it was that he blamed on someone else when it was brought up. A simple "I made a mistake" would have been what I would expect from someone who might make a great president some day.