The initial value of grid-template-columns is none, which ends up creating as many tracks as there are template areas, sizing them per grid-auto-columns.

Tab's Alternate Masonry Proposal instead uses an initial value of repeat(auto-areas, auto) which repeats auto to match the template areas (ignoring masonry-auto-tracks), and falls back to repeat(auto-fill, auto)... which is technically not defined atm, since auto depends on explicit placement.

What should the initial track listing be for masonry layout?