I can't really understand how you can read my sentence of "The File manager UI optimizes for file management tasks" into "Are you telling me that the File Manager is not an optimal UI for managing files?"
No, we're not saying that. File manager is specifically optimized for managing files.
What we're saying is that managing files != consuming files. File management is for copying/moving/sorting/creating folders etc., consumption is for browsing, filtering, consuming etc. The optimal UI's for those two streams of tasks are different.