Totally agree, conversation catalyst is a great way to phrase it too. This is very much the approach I've taken having had very mixed outcomes from trying to do just one thing or the other. I find using a simple, 100% self contained task that should take a few hours and then using that to kick start discussion has provided the best way for us to hire and screen people. We've found using a task that is very simple to get a working solution but provides a lot of scope for edge cases or growth to be effective. It allows the candidate to not blow a whole weekend on something for the sake of it but gives us obvious directions to take the conversation.

Communication skills seem to be held in much lower regard despite them being the key thing for effective day to day work. I can manage / handle working with someone who needs more time than a "rockstar" or hasn't memorized TAOCP if they'are able to communicate effectively. Outside of very specific roles, non-trivial software development is a team effort. It's usually extremely obvious within 15 minutes if a candidate genuinely gets what they've coded or is winging it.