As respected as he may be, he is entirely speculating from his worldview and not from a position of actually doing work with #nostr . C10k was blown away years (and years) ago with one server and 1m connections. That is certainly not his only point, but represents the quality of the analysis.
To understand scalability of what we have you need to noodle out (and test) relay mesh topologies.
My only point is, for anyone wanting to opine on #nostr future needs to be building