You can add more columns, of course, e.g. for a sidebar. That's the advantage over flexbox. Grid is great for whole-page-layouts, Flexbox' strength lies more in the smaller scope, like Navs or Lists.
Still would see it as a bit of an overkill for this specific use case and, really, nothing prevents you from using flexbox also in the larger scope of the page.
My understanding was that css-grid is recommended when you need to align in two dimensions, whereas flexbox is pretty fine to deal with one dimension.
Browser support is also slightly better for flexbox, not sure about performances.
You can add more columns, of course, e.g. for a sidebar. That's the advantage over flexbox. Grid is great for whole-page-layouts, Flexbox' strength lies more in the smaller scope, like Navs or Lists.
Still would see it as a bit of an overkill for this specific use case and, really, nothing prevents you from using flexbox also in the larger scope of the page.
Of course not. I was not stating that.