Path not appended when using UriBuilder.fromUri().path() with file scheme

See: https://mail-archives.apache.org/mod_mbox/cxf-dev/202001.mbox/%3CCAGRgoZhuKXoYW_JtxyDH%3Du7Qqqcbeo6-9BXa0dxB8L%2BiGB4J4g%40mail.gmail.com%3E

When calling UriBuilder.fromUri("file:///~/calendar").path("extra").build().toString() - the result is file:///~/calendar, without the "/extra" on the end. CXF 3.1 behaves differently (the /extra is appended).

I've requested clarification on the spec: https://www.eclipse.org/lists/jaxrs-dev/msg00773.html.