The specific tolerance within that 8-13ft range is driven by wave period. Long period waves lets us operate more towards that 13ft end because you can contour the waves.
Having said that, I'm pretty sure the much larger Monarch (their further future 50-100pax model) will probably have longer vertical supports on the foils.
In no cases are we contouring waves in flight. We fly straight and level. Typical flight altitudes are 10-30ft above the wave peaks. The waves are well below us.