Documentation of notify-delay appears to be out of date

The documentation for notify-delay says:

The overall rate at which NOTIFY messages are sent for all zones is controlled by serial-query-rate.

The documentation for serial-query-rate makes no mention of NOTIFY messages.

My understanding from https://kb.isc.org/docs/aa-01313 is that serial-query-rate used to control NOTIFY rates, but no longer does, so I assume that this is just an outdated reference, and it should now point to notify-rate

I'm also struggling to understand exactly what notify-delay does. The description says:

This sets the delay, in seconds, between sending sets of NOTIFY messages for a zone. The default is 5 seconds.

Is this defining the maximum rate at which NOTIFY messages are sent for an individual zone? i.e. if a zone changes twice in 2s, the NOTIFY messages will be sent 5s apart?