Interesting... Jim Putnam on YT always did mention "gravel regret"... in that using gravel in eastern US results in a lot of weeds because they get a lot of rainfall. So, I guess it's true. But, in the west, gravel is fine, because it's a bit drier.
I have areas that are gravel only (a small karesansui in the frontyard, one in backyard, and both side yards), and those gravel areas never get weeds.
However, my bigger 1-3" beach pebbles (far from gravel) gets weeds sometimes...I think because the gaps are larger, so the seeds can get a little sunlight and also reach the soil underneath to plant their roots into.