You are implying there is a singular network. There are a collection of relays on the internet. Each relay has it’s own business rules and may or may not accept your events. Each client may support some type of events.
Explain to me how you trivially saturate this protocol. That’s like saying you can trivially saturate TCP/IP by broadcasting packets.
Here's what I said, verbatim: "then you can trivially saturate the network, the clients, and the relays with bogus events."
What are you arguing against?