I have a couple of custom child themes I use. This theme only uses 4 files:
footer.php
functions.php
screenshot.png
style.css
I updated the version number in style.css, which properly displays in my MainWP dashboard… but it still continues to get flagged under the “Abandoned Themes” section and shows that is was “Updated 2284 days ago”.
If you create your own theme or plugin, it’s always a good idea, to give it a unique name. You can prefix it with your name, initials or whatever. So use “scoopy-custom-theme” for example.