This is only mostly true, they do subtly change some semantics. As a motivational example, it is possible to encode a colon in a header name in http2 but not i

This is only mostly true, they do subtly change some semantics. As a motivational example, it is possible to encode a colon in a header name in http2 but not in http1.1, and this does not violate the RFC which only blacklists "\0\r\n".