Should Plugin Folders Include a Blank index.php File?
WordPress scans all PHP files in a plugin’s root directory to find plugin headers. This allows you to have multiple plugins under the same directory, example
It also means that unused PHP files in that directory are wasting time and memory when WordPress is searching for plugins. One file will not do much harm, but imagine this is getting a common practice. You are creating a real problem in an attempt to fix a fictional.
If you like this question & answer and want to contribute, then write your question & answer and email to freewebmentor[@]gmail.com. Your question and answer will appear on FreeWebMentor.com and help other developers.