Where I have worked, the architect is the person who helps the key implementors work together smoothly, shares knowledge about the design, gives advice, and brings in other teams he knows can help.
It takes a lot of "tribal knowledge" about the various teams involved in a project to do this kind of thing well. The most successful architects I have worked with are the ones who have a lot of experience at the same company. They don't design the architecture -- they convince all of the participants in a project to collaborate on designing the architecture.
The people I am describing are more technical than project managers and are able to give informed advice on the architecture and the code, and often commit some of the code to the project in addition to the other project management duties.
It takes a lot of "tribal knowledge" about the various teams involved in a project to do this kind of thing well. The most successful architects I have worked with are the ones who have a lot of experience at the same company. They don't design the architecture -- they convince all of the participants in a project to collaborate on designing the architecture.