Don't worry, you aren't the only one, the tomshardware article had the same misunderstanding.

The only thing this change does is that the pads of the chip packages can be spaced tighter together, which allows the packages of the chips to be smaller sideways. It doesn't change the height of the chips.

And yet not only did the original article misunderstand that sideways isn't height, they also thought that making the chip packages narrower will directly lead to the phone getting slimmer.