> the work I do is so bespoke and unique and novel and important that I can't be bothered to estimate how long it'll take

This absolutely can be the case some of the time though. I've never pressed back on estimates of standard work but it can be a real bastard to have to work within the "process" when you are slaying a truly novel beast. Having some jackass pestering you for updates on how long it takes to climb the beanstalk and find the golden harp is just too much.