It isn’t stupid – it provides certainty. There has to be a cut-off point for proxies, pretty much all notices of meeting provide for that, i.e. proxies to the manager prior to commencement, if someone comes to the meeting they can bring it with them. The adjourned meeting is a continuation of the original meeting so you can’t restart the clock in terms of proxies.
I am not so sure of the numbers, but how many adjourned meetings are there?
Going back to the original query, the manager has got it completely wrong. There was no quorum, so unless enough people attend in person at the adjourned meeting there will again be no quorum and no meeting, which is what JGOWI said at the outset.