I'd put the initial fuck-up on Apple marketing, who used the UNIX trademark without license nor compatibily.

This was an attempt to repair the damage that had already been done, by passing the UNIX compliance required to become an official, paid, licensee.

In bigcorps, marketing can freely make false claims, and engineering is on the hook for delivery.

You are technically correct that this was a sales fuckup, but the shit storm would 100% be directed towards the “underperforming, delivery-target missing” programmers.

Isn't this a good example of engineering and management working together to make changes over multiple departments?

The engineers got time to asses if the project was feasible and what kind of support they need. Management fully supported them and made the other departments play ball and they made allies in other departments that helped them making the changes necessary.

They were asked if they could do a job and given the time and ressources to asses the situation. If they had any doubts they could've said no and let the legal department take over.

It's legals mistake. Ads have to be run by them. They should have caught it.