I just thought of this and it may not apply but it may be worth considering. It could be that shading with something that blocks sunlight by floating on the surface may possibly work the opposite as anticipated. The nutrients under the blocker could find their way into the rest of the pond stimulating more excessive growth there. So definitely not the same situation as laying a board on grass but if one does this the nutrients (& water) under the board are available to grass growing around the edge and this stimulates growth around the edges. With dye the shading is throughout the pond so it effectively limits the energy available for submerged macrophytes and phytoplankton everywhere.

To FireisHot's point of applying dye at recommended rates interrupting the bottom of the food chain, I have witnessed dye destroy the best trophy BG water I have up to now fished in Texas (I've not had the privilege of fishing Al's big BG). The pond was undergoing annual increases in FA production until community members complained of a midsummer FA float that forced action. That was 3 years ago and the dye continues and the fishing now sucks. So maybe there is some more reasonable treatment than the one the dye company recommends? I don't know. Is there a some formula that one can calculate the shading provided by a given treatment rate (grams dye/1000 cu ft or something like that)?

It isn't what we don't know that gives us trouble, it's what we know that ain't so - Will Rogers