The key here is the one minute limit on how they describe they are blocked. Everyone in the team hears that and there has never been a time when one or two people haven't offered to help the blocked person. This means that everyone is aware of what's going on.

The team do work with each other ahead of the meeting, informally, and its not unknown for someone to say 'Not blocked but...thanks to Paul I was able to get around this problem'.

Key thing is to not let the meeting become an hours' worth of detailed technical discussion with people sitting quietly at their desks doing nothing whilst two people talk at length.

By the way those meetings where one or two people are talking whilst a dozen people sit quiet have become known as 'Bear in the Chair' meetings, they are the kiss of death.