+1 for change it back, another point is that, this would not change and would not affect anything in the mechanics of the game, I hope that the staff will give a better answer than, "let's not change it back".
What positive does this change in happiness bring in addition for players ?
You limit some pokemons to be lent between friends and guild mates. (Pinsir, Lops, Diggersby...etc)
That is, if you don't go after these pokemons from today, you won't be able to use them, because nobody has the patience to keep increasing or decreasing the happiness of the pokemon in each trade.