The issue with harnesses and no cage is that in a rollover, where a 3 point ordinary seatbelt will allow your body to be forced over and towards the centre of the car (the shoulder with no seatbelt over it), harnesses with no cage means you'll be held nicely in your seat while your neck is broken.
That said, I think Clio's are pretty strong in rollovers aren't they? That's the thinking behind it.
Standard seatbelt + no cage = fine
Standard seatbelt + cage = death
Correctly mounted harness + cage = fine
Correctly mounted harness + no cage = death
Incorrectly mounted harness + anything = death
Correctly mounted harness, cage & Covid 19 = death
What about correctly mounted harness + neck brace + no cage ?