Exactly! Coding challenges are not about miraculously finding the right solution, which is boring (and extremely suspect). They are about describing a path from the problem to the solution, and dangers and pits along the way.
Given that some companies now have candidates do them on fully automated web pages, it's pretty clear they are often just about getting the right solution, and nothing else.
All job interview steps are "simply trying to filter out the pool of candidates". If it is the filter that removes the most people, that actually makes it the most important part of the interview process.
