Yes, it polls. Most functions are quite fast, and fine to just poll, and it's quite convenient to be able to bind to functions when needed.
But it's all tradeoffs - in our app we have a few that aren't - for those, we profiled to find them, and added a bit of code to the functions to cache the return value.
But it's all tradeoffs - in our app we have a few that aren't - for those, we profiled to find them, and added a bit of code to the functions to cache the return value.