Yeah I was considering all issues rather than just anchor. Another source [1] gives 100-200 incidents per year with 16% as anchorage, so 25 a year (from anchors alone) is probably a safe estimate.

I think most of us thought these incidents were exceptionally rare, so a recurring pattern of incidents itself would be suggestive of nefarious behavior. 'Oddly' enough the frequency datum was omitted from seemingly every single article on this topic.

[1] - https://www.iscpc.org/publications/submarine-cable-protectio...