there is a difference, wich makes it illegal...
When you duck or 'double-duck', you go faster than walking, but slower than running.
When you do it with scroll, you go at the same speed than when you are running or even a little faster
EDIT: You can solve this problem by:
Either using an "anti-scroll" plugin, wich makes they only can bind scroll for jumping
Using and anti-cheat that blocks it