Hello Adsto
I would guess trimming is recommended so that the column is nulled. In that condition back in the tail a small roller (feel roller) sits in the "V" in the middle of the cam dwells on the feel cam, because when the EFS operates & increases the feel force by 4 times it could attempt to pull your arms out if the roller was out of the "V" by a good way.
The step up in feel by 4x would tend to null a column that was being held back to maintain altitude at decreasing speed. That is it would move forward away from you, so trimming would take away the surprise as the EFS operates.
Hope this answers your question