Creatives are often asked to work in a ‘collaborative’ style - by both clients and account people - and we always say yes. Not only does it sound modern and innovative, if you say you don’t want to work collaboratively you just instantly sound like a jerk.
But a lot of the time ‘Let’s work collaboratively’ just means ‘I also want to be a creative on this one.’ Simple as that. The person saying it thinks they have ideas about what the concept should be, and they want you to go along with them/just jazz them up a bit. Sometimes their ideas are good, in which case you should. But sometimes their ideas are shit. If you say they are shit, be prepared to be accused of being un-collaborative.
NB: When a creative says they want to be collaborative, it has the inverse meaning. It usually means they don’t really give a shit about the job, and so they’re happy for you to give them the answer.