Since October 2023 it’s no more possible to create a document directly from the Template Gallery, if the user is not the owner of the file used as template. Before was possible and it’s still possible from Drive or Document, so it’s not a security reason to have introduced this limitation. In addition this limitation doesn’t work if a user open the Template Gallery from a cell phone (Android) because the request to create a document from a template, automatically open the Drive app and works.
Idea: let new file creation directly from the Gallery even when the user is on a computer, as it was until October 2023.