I believe he meant for relevant skill employment assessment from EA, which is, unlike ACS, an optional add on for EA migration skill assessment.
Well, last time I checked with EA, they said it was optional byt "highly recommended" to avoid delay in visa processing stage. However, that is few years back, so you should send an email to EA now for an update (and please let use know what they answered).
Here is the reply from EA that I received few years back regarding this matter
http://www.migrationdesk.com/thread...skilled-employment-in-engineers-australia.45/