In the case of an advance, landing first with the heel allows the foot to gently roll forward from heel to toe, keeping the movement fluid. In the case of a lunge, it can arrest the momentum of the lunge so that the fencer does not continue to move forward after completing the lunge. This can also be seen in the case of a retreat where the fencer stops quickly and needs to change direction to initiate an attack or advance. This is achieved by using the heel as something akin to a break, arresting all momentum and allowing the fencer to change direction quickly without drifting (this will still require the back leg to be somewhat positioned to the rear of the rear hip). As the sabreur becomes more experienced, footwork like the hop, skip, and jump will round out their movement and see them vary their dependence on heel and toe for points of contact.
Why should it be the heel that touches first?
In the case of an advance, landing first with the heel allows the foot to gently roll forward from heel to toe, keeping the movement fluid. In the case of a lunge, it can arrest the momentum of the lunge so that the fencer does not continue to move forward after completing the lunge. This can also be seen in the case of a retreat where the fencer stops quickly and needs to change direction to initiate an attack or advance. This is achieved by using the heel as something akin to a break, arresting all momentum and allowing the fencer to change direction quickly without drifting (this will still require the back leg to be somewhat positioned to the rear of the rear hip).
As the sabreur becomes more experienced, footwork like the hop, skip, and jump will round out their movement and see them vary their dependence on heel and toe for points of contact.
Stop talking
Stop being insufferable
Even more talking to come ;-)