To the best of my understanding the EVENT PB only interacts with the ACMS system and not the CVR. To keep CVR recordings the CVR must be swiched OFF, either by means of an installed switch, or by pullng the respective CB.
To imply that the crew was trying to cover their actions up by not reporting the incident to ATC is in my opinion quite speculative.
I understood from the report that ATC informed the crew quite soon. I think that the crew never having been aware of their error is a theory which lies better with me.
rgrds