A better (?) solution would be to have the step sloping back slightly. That would give the player relief outside the bunker.Is there, I wondered, a remote possibility that a ball could end up on the bottom step slightly overhanging its edge and therefore be in the bunker? A complication to be avoided, I further wondered, by making the last riser slope forward a little so that the edge of the step is sufficiently outside the edge of the bunker to ensure part a ball couldn't be inside it?
Finally I wondered if I was being absurd in even thinking like this and should go and do something useful around the house.
But do you consider the bottom step to be 'touching the sand'? If so is the eco revetting also 'touching the sand'?