Another approach (what I assumed would happen) is to have each group's logic independent, and not cascade. So it doesn't matter if I've already assigned the ABC

Another approach (what I assumed would happen) is to have each group's logic independent, and not cascade. So it doesn't matter if I've already assigned the ABC group, typing a single A keeps the ADE group white, up to uniqueness. I think the biggest issue with group assignment is the fact that you just can't type while the wrong group is selected. I don't care what tools you have for narrowing down letters, if I see a solution in my mind, I should be able to type it out like I could on a piece of paper. Assignment feels more like adding flags in minesweeper (optional, helpful) than part of the solution.