Honestly, a good PR should have a very clear description of the idea and a sample implementation, and then a trusted core contributor re-implements the fix on his own. But Github users are entitled and spoiled by Github-marketed commercial software, so they will rage at this.
An issue usually doesn’t have the code for implementation of the solution. Yes, very often patches are attached in comments, but they are not required and usually attached by other people, not the author.
