If the author has set the file to Read-Only, "Edit" in Teams should open the File Read-Only
I have some Excel files, which are used to calculate something based on the content of one cell. To prevent the formulas to be changes I have set the file in Excel as "Read Only". If the file is stored in Teams, and I open them in the desktop app, I can change the cell which the input for my calculation, the sheet calculates, and I really have to consciently save the file. If I click on the "Edit" button to open the file in the Teams App, it will open the file in rw-mode - which will generate a new version, and I will not be able to track, if I have changed the formulas, or just did a calculation.
So, the Edit-Button should open the file Read-Only, as I set it as Read-Only.