I enabled theme debugging in services.yml file and I added a template file. Following is what I see in file name suggestions:
Here's new file's name:
The file is not recognized. The page is still rendering from
<!-- BEGIN OUTPUT from 'core/themes/stable/templates/layout/layout--onecol.html.twig' -->
So, I tried adding layout--onecol.html.twig file in my custom theme. And this file is recognized which means file names with * in suggestions list are not working, but names with x are recognized.
I believe they should work in opposite way.