Yes you can have non destructive FX but when it comes to copy/paste/cutting/resizing it's creating new files on the hard drive so the SEQ is getting bigger and bigger. Where as if it's just referencing the original file, meaning that any section of the file copied will still be able to be adjusted out to it's original length. This works instantly and smoothly without having to wait for RB to re-render the files because a bit has been cut out of them, so if one file has a section cut out and moved somewhere it will need to render 3 new files and delete the original one.
Using NDE in RealBand would give you instant track generation, quicker than Biab ! as it's using the original source file sections that will remain untouched and give way more control in the editing of what you need. The SEQ files will be very small like a frozen SGU and has all the track section data.
When you drop a file into RB it will create a copy of it to the Temp folder then write it to the SEQ when saving, all this is unnecessary in this day n age.

The reason people use Biab then RealBand or DAW is Biab is quick at generating up the song, quicker than RB and BiabVST, but Biab does not have good DAW editing. All this can change with RealBand and BiabVST giving INSTANT generation of tracks.
If my hard drive didn't fill up so many times and Windows stop working from all the wav files that were being created I would not have looked into all of this.