The pro 600 is equipped with Philips electronics. Standard that 240V system is not dimmable. In horticulture we hardly ever dim. If we do we use Dali systems (external and through computer systems). You shouldn't need to dim a system anyway
I was told that the ballast electronics are set up for dimming, but for whatever reason they decided not to bring the controls out. If they were dimmable, I would buy two of them right now - I have a rectangular space that is a bit too small for (2) 600's side-by-side, but could use a bit more than 400's. I also like to buy equipment with the highest degree of flexibility possible because I am forever tinkering with my setup.
Henry Ford's philosophy that "You can have any color you want, as long as it's black" costs you customers in this day & age!