The moment you begin to introduce this other element, you are bringing a psychological element. The invitation should be in the message. We believe the Spirit applies the message, so we trust in the power of the Spirit. I personally agree with what has been said in the question.
I found this absolutely fascinating! It's a great read and really a nice little piece, regardless of where one is denominationally right now. I strongly recommend to people who already feel that altar calls (that don't start with "The gifts of God..." tend toward psychological manipulation