[T-bird_se]

Also I don't believe as many ppl leave their entire movie library (which could be hundred to thousands of movies) to be listed in Ember

That is just too ridiculous, it would slow down Ember, and make it hard to manage the thousands of movies, and could be accidentally get Scrape All again.

There might be a few that do this..

But I believe most ppl just scrape the movies then move it out to another folder, drive, server, or NAS..

I belive you are wrong, I think that's how most users use it
If you just scrape All you have no control of what to download, so why use Ember at all, let Kodi do the scraping?
Personally I constant rescrape new movies for more or better artwork or updating info like votes, rankings etc..