The mental gymnastics around them not being visas come down to this:
You don't need an 'electronic travel authorization' to enter the country. But commercial carriers may get heavy fines if they let you board a vessel into the country without one. But if you somehow did, the Border Police can't use your lack of an ETA against you.
Since any boarding rejection happened outside of the EU, rights you would have under EU law may not apply. Extra-territoriality at its worst.
IE: If you drive, by personal car, and you're a citizen of a visa-waiver country, you may do so without an ETA.
In other words, Americans, Brazilians, and Australians will still be free to drive to the EU without a visa after ETISA is implemented. I hear Tesla is working on the technology. Or you could charter a private jet. These rules aren't for *those* people, just everyone else.
When Canadians got caught up in an ETA mess, sometimes the workaround was to fly into a US border state and then drive across the border. It's a real mess when someone loses their Permanent Residence card overseas: they can't fly to Canada without their card, they're ineligible for an ETA, and the Canadian embassy acts slow when it's not a citizen that lost their passport.