Is EOSE mandatory?

[Aspie96]

When what was previously NIP-15 was merged into NIP-01, the following was imported:

["EOSE", <subscription_id>], used to indicate the end of stored events and the beginning of events newly received in real-time.

This previously was not mandatory, of course, since it wasn't in NIP-01. Now, NIP-01 says nothing on whether relays are required to send this message once they have sent all events.

Is sending the EOSE message to be understood as a requirement for compliance?

(Of course, one should send it regardless).

[alexgleason]

Clients can't assume they will receive an EOSE, but relays need to send it. For performance reasons, as a client you often want to only get existing events and then close the connection. You don't care to poll for upcoming events. Without an EOSE, you don't know when to stop listening, and can rely only on a timeout. So yes, it's considered essential.

[Aspie96]

If it's considered essential, and understood that relays MUST send it and are non-compliant if they don't, I think this should probably be clarified.
Right now it's just reported as something relays "can" send.