This feature request has been declined by the feature team. However, the feature team is working on design changes to better help differentiate Teams files.
Which hopefully will help alleviate the confusion users are experiencing when when trying to identify SharePoint files versus Teams files.
-WarrenSimon Cousins commented
We love Teams; we love SharePoint /Documents. We HATE that Teams makes a folder in our SharePoint /Documents for every Channel. It leads ONLY to confusion and mis-filing. Please don't force folder creation in an otherwise carefully managed and curated documents hierarchy.