I’ve started getting a message about unrecognised file wp-includes/js/tinymce/wp-tinymce.js.gz in Shield.
This file doesn’t exist in WordPress but I’m just wondering why I’ve suddenly started getting warnings about it? I know I can “ignore” it, but that’s not the point really.
According to this code, the .gz file is used to serve a pre-compressed version of some JavaScript files related to TinyMCE. Deleting it won’t cause any issues because there is a fallback method below that line, which is used if the .gz file doesn’t exist.
As far as why it’s done this way (and why this change was undone in WP), it looks like it’s a performance enhancement. You’d have to look back at the WP commit history and the associated ticket(s) for more details.