I talked to a few people and if you have good circulation in the pool with plenty of turbulence at the bottom the main drains are supposed to do quite a good job of minimizing vacuuming.
Sorry but I think these "people" are just misguided and do not understand hydraulics very well. I have main drains and I can tell you they don't do anything. This is especially true of dual main drains with safety covers. The reduction in entrapment also reduces the force of the water in any one direction (done on purpose) so they do move anything very well. That is why they lower entrapment.

Perhaps you should read this article and watch the video if you still do not believe me:

http://www.poolinspections.com/manua...out-drains.pdf

https://www.youtube.com/watch?v=0IOUGhuKkSM