Yes but than the plan of action takes form of authority. Which is the point that Engels makes.
It is an extension to the libertarian notion of authority that Engels makes.
Suppose you and your comrades are are at a party conference in another city, and, in a wild bout of anti-authoritarianism, you’re talking among yourselves which restaurant to go to instead of following party orders. Maybe it’s just an oversight, the responsible buerocrat didn’t do their job. Anyway the obstacle is not insurmountable, the choice is not very contentious, some people have preference, one’s a vegan, but in the end you all agree that Mexican is a perfectly fine choice.
Then, out of nowhere, a KGB agent appears saying “Now it would be a shame if someone changed their mind about eating Mexican and would need to be sent to Gulag, would it, after all, we can’t have a decision without subsequent imposition of authority”.
Then noone is required to take the delegate serious.
The delegate is taken just as serious as the council they represent. They are, after all, the representative of that council. If you ignore what the delegate says, you’re ignoring what the council says. But the authority is that of the council, not of the delegate.
The definition of anarchists
Council communists have a compatible definition, btw. It’s only Bolsheviks and their descendants who disagree because they can’t stand workers actually having a say in things, see the Trotsky quote before. That is authoritarianism. You can’t declare it away by playing semantic games.