Consider this.
A and B are two sides of a "thing".
50% of players want A
50% of players want B
If the Devs implement A or B, then 50% of players are disappointed.
If the Devs implement a toggle that players can choose between A or B, then 0% of players are disappointed.
Why would you oppose an option that would result in 100% of players being able to play how they want?
It may not apply to the specific functionality discussed here, but as a rule, it's usually not so simple.
Allowing players to choose A or B means your game has to support A
and B.
So players who want A do not get A: they get A with support for B.
Let's get an example, from the RPG sphere.
Some players prefer playing with a controller, others prefer mouse & keyboard.
Nowadays, most games offer support for both... but development ressources being what they are, they don't provide two completely different control schemes.
They usually go for the more limited one (controller). That means you can't click on an item to pick it up, you move (with the mouse) next to it and press an "action key". Your active skills slots are limited to what a controller supports.
So while the option to play with mouse and keyboard is there, it's been heavily impacted by the need to support a controller scheme.
I don't think an "Undo" button option would have such design consequences, but it might?
As some have said, not abusing "Undo" to explore your immediate starting environment could quickly be considered substandard play. As a counter to that, the devs could decide to have the game start with a city instead of a settler. That would be an example of how support for the option would impact both sides.