The claim, as I understood it, is not that other compilers provably have no bugs, but that maintainers (and the whole community) react differently when one is f

The claim, as I understood it, is not that other compilers provably have no bugs, but that maintainers (and the whole community) react differently when one is found. If you demonstrate a bug in gcc or rustc (or one of their base libraries), it is a major issue that will at least get documentation and a warning (and likely a quick fix). In Julia, even documenting it may be relegated to the middle of the todo list.