This depends a lot of the size of the project and company.
Some teams may work more on a model where they just have to deliver X, where X is some high level business requirement.
In such circumstances it might not be unreasonable for the project manager to make decisions about which particular bells and whistles to include in the version 1 deliverable etc.
And there's no chance you could, instead, just get up and walk to where the PM sits, or call him/her via phone, or use IM, or just send an email, and accomplish the same end?
To me, it sounds like a false dichotomy to say that you either sit together and have rapid communication OR you sit apart and are forced to wait for a weekly checkup meeting... surely there's a continuum there??
"hey, feature x.y.z is actually a pain, now that I look at it closely. Can I email scrap it?"
"scrapped. "
Way better than spending a couple of days working on it before a weekly checkup meeting.