Part of the beauty of pointing people to the sufficiency of Christ in this way is the lack of manipulation. It offers freedom to the listener.
They also talk about the particulars of assurance. It's not for the general or vague "everyone" but there is a "for-you-ness" they explain. It directed personally.
They talk about the tangible means, earthy means God uses to point to our assurance outside of us. God uses means to comfort us, not just these abstract ideas, but sensory means.