In my opinion takara made those chocolates from his father recipie and while they were delicious (he is a world famous chef) his choco were chosen over his father's
So thts y he's happy
It was Dad's purchased chocolates in the box (Takara never boxes test items), he wanted an opinion on whose creation was better. The chocolates tasted better, but Izaki still loves Takara's previous test items.
I feel like this is the first time an extra dramatic shojou like situation has happened in this manga