Hello, I'm the co-editor of the multicol specification. Looking at the data for multicol, pretty much all of the issues detailed as multicol problems are actually fragmentation issues. The break-before, break-after, break-inside properties are part of the CSS Fragmentation specification, and general fragmentation properties not specifically for multicol. See: https://www.w3.org/TR/css-multicol-1/#break-before-break-after-break-inside

There doesn't seem to be a more general page for fragmentation (which applies to print contexts as well as multicol), though the properties are there due to the MDN data https://caniuse.com/?search=break-inside.

Would there be interest in fragmentation data separate from multicol? If so I could submit a PR for that. I think it would be clearer for people looking at multicol if the true support for that spec was indicated.