Writing 8 separate files simultaneously is much more taxing on the media and more likely to produce write errors.
Is that actually true? If so. its never been a problem for me using Zoom F8, Roland R-88 or Tascam DR-680.
I got that from somewhere in Sound Devices' literature. It may have been in the 788 manual when talking about writing to the CF card.
It is definitely true for the older SD633. When that was new, I was having lots of issues trying to write separate files and was advised by SD to record poly files, after that I never had problems with the SD633. But with the Zoom F6 and F8 I never have had any issues with writing separate files ever. My Mix II 6 is "lightly used" but I don't remember any file issues with it, either. So I think it was an SD issue and is maybe solved.
Jeff