Tank to tank combat on an engagement level had always been taken into account because this was supposed to occur. In fact, this occured so often that there is your example of Villers Bretonneux.
So it was always taken into consideration in the conception of a tank, because anti-tank guns were the weapons of tanks. One of the earliest mention I think is the ...
Time: right after WW1
A "good antitank capacity" was important in tank design already in 1920-ies.
A duck can fly, walk, and swim, and does all these poorly
A tank is a compromise between weapons, armor and mobility. It is thus relatively expensive to make and operate.
Therefore you don't want to fight enemy tanks with your own.
You would rather ...