Maybe a combo of technique, rigging/equipment set up & sail. Sounds like your board is newish and FSW
suitable for Botany. Modern sails have greater wind range & more efficient design (obviously). As well
was it closer to 15 knots or less inside? Planing straight off the beach is hard for most.
You will find it tiring the first few sails at least, it's a different fitness also.
If you are posting provide more detailed info so your Q can be addressed specifically, or not