Yes, but then nobody implemented the SGML definition of HTML correctly. According to the standard, browsers should have parsed <a href=foo/bar/baz>qux</a>

Yes, but then nobody implemented the SGML definition of HTML correctly. According to the standard, browsers should have parsed <a href=foo/bar/baz>qux</a> as <a href="foo">bar</a>baz>qux</a> since it did not only include optional closing tags, but also short tags. (This is incidentally why several SGML-based HTML validators used to complain about "end tag for element A which is not open" in the presence of href attributes without quotes.)