I am also not a network expert, but here's my read.

It seems like he's saying that Nostr's main scaling issue will be the ability for relays to keep up with the data transfer rates as the platform gains more and more users.

In order for Nostr to be heavily decentralized, anyone needs to be able to run a relay. This is so that there isn't any one point of attack to censor the network.

The problem is that most home networks are limited to gigabit internet speeds and the current Nostr demand is already stressing the network at relatively low user numbers.

He might be suggesting that a solution would be corporations or large groups with higher bandwidth infrastructure running relays. Which would then move the network towards the centralized side of the spectrum.