None of the GPTs can do column-based math, because they can't see columns. Byte pair encoding doesn't preserve characters. "1", "3" and "13" are all different tokens. This is also why GPT can't rhyme.
Do you know how previously unseen numbers in the prompt are encoded, probably the same way? Then GPT3 can not do any math at all, unless the specific numbers were seen before?
The quote above referred to exact copies of the problems, not individual numbers. And the abysmal success rate on four and five digit numbers does suggest it has trouble on rarer numbers.