My experience with a leadership consultant:
We had a consultant come in and talk to us about leadership and management. Meetings was only a small part of it, but the concepts from my experience should also apply to your situation.
The leadership consultant had us come up with some ways that we can build better relationships with the people who work for us and with us, and although it seemed like busy work, there were some things that we took away from the experience that had an overall positive impact on our working relationships. Maybe we didn't all become outstanding leaders at that moment, but the seeds were planted...
The consultant's role was to guide us and help us come up with a plan that worked for us, and the consultant you're meeting with should hopefully help and guide you in coming up with a plan that works for you.
Why do companies do this?
Companies sometimes do things like this as experiments. About that big long rulebook you found that no one enforces, well, it's an example of a failed experiment. This terrible idea didn't seem so terrible when it was thought-up, and luckily the idea died simply because it was long, boring, and most likely very dry reading.
Consider that management might be smarter than you give them credit for. Maybe they chose to forget about that very big rulebook on purpose, since they know it didn't work.
Use this as a learning experience; a chance to collaborate and improve
Thus, it's very possible that the code of conduct teamwork exercise is intended to encourage you to work together to build a framework for meetings, which you, as a project manager, can then use to tailor your own meeting-style. So don't think of this code of conduct as a list of inflexible rules but more as guiderails to help you navigate the meetings successfully while still tailoring them to your unique problem and situation.
This is the difference between a framework and hard-fast, inflexible rules. The framework should give you just enough information to start you off on the path to success without dictating the finite details.
For instance, if you hold larger meetings than other project managers, and clients are involved, then perhaps what works for you might not work for others. The goal of the exercise should be to come up with ideas that will make all of your meetings successful, yet still allow you the breathing room you need to adapt to change.
If you asked me today what we talked about with our consultant, I don't fully remember. In the end, this experiment should be successful even if you forget all about the worksheets you filled out with the consultant. Why? Because the ideas are your own, and hopefully they'll become second-nature. :) And if it fails, then hopefully you and management have the foresight to move on and try something different. Hope this helps!