Unnecessary? Hardly, unless you think scanning unnecessary items each scan is a good thing - hint - it is not.
Movies in their own unique folder are excluded from a scan IF you tick the boxes next to:
Scan My Library Automatically
and
Run Partial Scan when media it detected
That means if you add ONE movie - that ONE movie is scanned, not the entire Plex Library System.
Having movies in their own unique folder is very necessary indeed.
Also, if you drop Local Media Asset to the bottom of the stack of active agents it’ll stop giving priority to bogus embedded Title Fields in MP4/M4V files and blowing your matches when Plex prefers the bogus embedded Title Field, even over a perfect file name (if you have any).