Tbh, I think it has to do with not having the manpower to do the coding for weird talents. The actual game came out with quite a few major bugs.
Most of the talent are just free stats that don't take ages to code multiple line for them to work. They are just simply number modification.
Extra range, extra damage, extra health and other stuffs feel like variables that are already in the equations, just set to 0 instead.
And some extra stuff are just small if case like Execution is probably a small if case on checking death. something like if (turnKillCount < 1 && executioner == true) gainAP(2); when the char deals damage and it kills.
And with all those variable set in stone, they probably don't want to add anything yet that will introduce more bugs as situational yet interesting talents aren't simple line of code like Executioner and even The Pawn (It's probably an increaseMovementDistance(movementSpeed) at the start of the turn since the game track that when you spend an AP to walk).
So if you plan on suggesting they do something, make sure it's something that won't take more than 1 or 2 line of code to enable and will not mess around with other variables already in the game.
The easiest one we can get is something like "Alchemist, craft 2x as much potion" where the game will just have to alter the amount of item obtained or even something like "Grenade explosion deals more damage" since grenades already have their own damage formula and that kind of talent is just adding variable.
