[Terretta]

> amusing that they've decided to refer to this as masonry layout

They haven't decided this. Keep reading!

TL;DR:

Perhaps the best syntax could be grid-template-rows: none; to convey “please do not give me any rows”. Sadly, it’s too late to use this name, because none is the default value for grid-template-* and means “please give me only implicit rows, no explicit ones”.

Instead we could use the name off to convey “please turn off the grid in the row direction, and give me only columns”.

    grid-template-rows: off;

But do expect the name of this value to change in the future. And perhaps prepare for a future where we call this “columnar grid” or “Grid Level 3” instead of “Masonry”.

[rezonant]

This is creating a mode of grid where we say "it's not actually a grid" and is my biggest problem with this philosophically. It makes more sense to treat it as it's own display type, where the row/column targeting don't exist. It's not just that row targeting doesn't exist, it also makes no sense to target columns.