Agree with you that customers might sometimes feel trapped by specifications. Many people can visualise old system, and often you do not just reimplement old system, because there was a reason to do it better.

I found in these cases useful to write my understanding of what specifications are, and sent them to comment, so users do not need to start with blank page. And is easier for them to comment/criticize if somebody else (me) wrote it.

Also, after writing "draft specs", I can either continue with another project, or analyze design possibilities of this new one, while ball is on the user's side.

Yes, specs are important. And as they say, "if something is important and you want it to be done correctly - do it yourself".

pmas
To make errors is human. But to make million errors per second, you need a computer.