Easing off of the throttle is the most ambitious way to ease the trimmings. It all depends on the grass type also, as Bermuda grass does leave a mess.........Zoysia not as messy. Tall fescues.......leave larger clippings.
Wind shear will throw debris into most pools with no sidewalks or large bordered walkways, so trimming counter clockwise is how I achieve cleaner pools. The combi edger that i use isn't by any means a cleaner tool to use. They are all messy and will cause dirt to throw.
The real thing about the pools where i service..........the concrete is gravel embossed and those little rocks will fly......and the remainder is a old product called Bowmanite. Stamped, dyed concrete designs.
Rarely do I see newer in ground pools being installed here. The cost of cleaning and leaves is way too much for the average home. Those that can afford the cost, will not sweat a little bit of grass............you will get more soil in the pool walking across the concrete and getting and wind blow versus what the line trimmer will do.
If customers are excessively anal about a little trash, then maybe this account needs more fees involved.
The most thing I worry about in servicing these lawns is not getting iron prills in the pool.