On Benchmarks and timelines: I agree that 2.2+ was not widely available for many years due to the update cycle of linux distributions, but at the time nginx wasn't in the distros... so it become a thing where people would yum install apache2, get a 2-5 year old version, and they would benchmark that against an ngnix from their latest dev download.
The original work for the Event MPM started around 2004:
http://mail-archives.apache.org/mod_mbox/httpd-dev/200411.mb...
The version in 2.2 was mostly focused on Keep-Alive requests. Apache 2.2.0 was first kicked out on December 1, 2005.
To go beyond Keep-Alive requests, is a set of features/patches called "Async Write Completion". Much of this work was done in 2006-2007 by Graham Leggett:
https://mail-archives.apache.org/mod_mbox/httpd-dev/201510.m...
Timing wise, most of that work did not find its way into a stable release until 2.4, which came out February 17, 2012. This is the date the article references.
