We'll probably have to wait until they fine someone a zillion dollars to figure out what they actually meant.
The distinction is accountability. Determining whether a human decided the outcome, or it was decided by an obscure black box where data is algebraically twisted and turned in a way no human can fully predict today.
Legally that accountability makes all the difference. It's why companies scurry to use AI for all the crap they want to wash their hands of. "Unacceptable risk AI" will probably simply mean "AI where no human accepted the risk", and with it the legal repercussions for the AI's output.
In reality, we will wait until someone violates the obvious spirit of this so egregiously and ignore multiple warnings to that end and wind up in court (a la the GDPR suits). This seems pretty clear.