Only SMF uses XML and SQLite behind the scenes. While that is a poor choice of configuration format, SMF is considered the Golden standard which all others try to re-invent and re-implement (not invented here syndrome), because SMF has been working reliably for more than a decade, and all added capability doesn’t break backwards compatibility, so an SMF manifest you wrote ten years ago works without modifications on the latest and greatest nightly build of illumos. That’s system engineering as opposed to haphazard hacking. I use drivers in the latest illumos from 1995 and they run without recompilation or modification. I’d like to see GNU/Linux pull that one off.

As for \t not working in vfstab(4), it’s simply not true, as all my vfstab(4) files use the [TAB] characters to line up the fields.