depends on the type of job of course - some work with earlier feedback, some unnecessary, but my general thought would be that often rather than getting 30% feedback is worth getting 0% clarification - ie when getting the job make sure you pitch it back to the instructor, to make sure you’re 100% on same page, before starting any work at all. Often I feel the 30% feedback request is really just a ‘is this right? am I doing what you asked for?’ which is another way of saying ‘I wasn’t 100% confident I understood the instructions, so wasted 30% time coz wasn’t comfortable seeking clarification at the start (or didn’t think to)’. Put another way, take time at start to think thru all parts of job, and if you need clarification ask as soon as (reasonable after) you think of it.
Tho I agree that in other circumstances genuine 30% feedback can be good, eg to show people what their very clear instructions are leading toward is not what people hoped…