It is *not* open to everyone. That would assume everyone is able to be there 100% of the time.
"Open to" means they can access it if they want. Sure, not everyone is going to be there all the time, but they can be there at any time they choose.
A log solves the problem quickly, simply and easily. It's not changing any of your processes, but makes the community more inclusive.
It goes some way towards solving the problem, it's very difficult to follow conversations in logs though, so it hardly solves it completely. I don't think it's a significant problem, though - the discussions aren't important, it's the conclusions that matter and those are all made public anyway. I've chatted to plenty of people about the plans in private as well and I certainly don't intend to make logs of those public, but it doesn't matter because nothing actually gets done in private, it's all just talk.