wordpress similar/related posts by title

I know that there are many plugins which does this. but I am wondering why all plugins only get related post by tags and not by title?

what is an efficient way to retrieve all similar post only by title in the single.php. for example, if I have two posts whose title are “speed up wordpress loading time” and “speed up wordpress backend”. then in one post, the other one should be related and shown.

I can think of a way to do that, which is to get all posts under the same category and using similar_text() to compare each title against the current one. then order the result and show the top ones from the list. is this a good and effecient way to do that?

any suggestions? please attach a snippet of code if you have a solution.