I think you are both right. The key may be "large transport aeroplanes". It has been my (unscientific) experience that smaller GA jets which are likely to be operated privately, possibly even single pilot, achieve unfactored landing distances relatively easily if flown right. On the 737 it was not that easy and required everything to be done just right: virtually no flare, exactly on speed, max braking etc.
I believe (but cannot prove it) that most GA manufacturers add a little fudge factor (probably by telling their test pilots not to try "too hard"), in order to protect against future runway overruns by private operators, including single pilot, owner-flown ops.