Step and thrust vs. thrust and step

I was having an interesting cross training session with my step brother who does olympic fencing at university and I came upon a significant difficulty in countering a habit I'd learned across a multitude of styles; stepping first and thrusting second. He kept trying to correct it and it was most difficult for me to counter. Every weapon style I've done teaches either coordinated movement of the feet and hands or a slight lead by the feet in order to move the body mass first. Empty hand is slightly different as you're not thrusting at an opponent using a weapon but this style of movement makes sense to me as you're moving the largest mass first, are able to close and correct the angle and distance of hits while in motion, and especially with large/heavy weapons use your body to drive the weapon's momentum and then thrust it with the arm(s).

So much of weapons is transferrable and a lot of other training plugged right in to fencing, especially the sue mai gwan techniques from wing chun. The fact that this one thing is inverse really makes me question. Can anyone explain why olympic fencing would teach the thrust mechanics in reverse to all the other weapon systems I've trained in?