The purpose is to have the algae exposed to air and to maximize the surface area. You achieve this by using a surge bucket and gravity.
People do construct vertical turf scrubbers utilizing a vertically mounted screen with a pipe dripping over it, but constructing one of any kind of large size is problematic.
Truf scrubbers take up a lot of space and are not practical, hense why people use macro algae refugiums, but if you are looking at 300+ gallons of space for this sump it is something you could do.
If you search online, there is the standard reef related hooplah with idiots arguing to the nth degree blah etc. There is a company that tried to take control of the idea and sell a product, when really it is just a biological process.
The truth, I think, about the turf scrubber system is that it isn't really viable for 99% of users and which is why you don't hear much about it.
I just mention it because it is something I thought would be fun to try out
Here is a sample I found quickly,
