I don’t think they gave it too much thought initially. I think it was rather a “but what if a player doesn’t take one element to the fight?” - “well, they don’t deal damage of that element” - “but that places them at disadvantage, we need to compensate” - “well, so let’s make it that the damage stacks”. That’s it. Note that the mechanics is from ancient times and I don’t think it ever changed.
Why I think it was a default way to play the game? 1. There’s 5 elements and 5 hero spots. 2. It’s a bit counterintuitive at first when tile of non-used element deals no damage; it’s making certain matches on the board useless, a bit strange for something that is a 3-match game. At least I was very surprised to discover that when I did it first time. For matches not to be empty and useless you need to bring rainbow. 3. Classic heroes (which were the only heroes available when the mechanics were created) did not have healers of all colors, tanks of all colors etc. Colors’ specifics were rather thematic (and kinda still are) with fire heroes bringing more attack buffs and dot, yellow bringing blind, green bringing attack debuff etc. Meaning you needed to balance them to cover all the functions. 4. Fighting with rainbow makes the matches longer. Longer matches are essential to bringing out strategy elements out of this game. It allows slow and very slow heroes to fire, it allows to work on your timings, and it doesn’t mean that if your heroes finally charged up likely the tiles already won you the match. Stacking makes this game binary - either banging your head against the wall until you die or you make enemy heroes explode like popcorn. It doesn’t feel like the game is meant to play like that. Of course noone forces using rainbow, but my original point was that the longer matches that result from rainbow currently place defense at unfair advantage somehow. So the matches tend to be longer (because you can fire a healer, or attack debuffer etc as opposed to no-tile stack fights), but you still lose because without tile damage from stack you just can’t get through.
Of course it’s just my assumption and ‘feel’ I get from the game. If we were to argue over that point, I think there are also solid counterarguments to that point (existance of elemental defense debuffers or elemental links).
Generally I don’t think they gave the mechanics too much thought because they couldn’t foresee how this game would progress and grow. Problem is we still play the game by these old rules even though it is much different from what it used to be.
I didn’t want that indeed although that’s good to see the discussion going. I am am him, btw