I agree. And this is one of the problems with trying to use the argument of "relativism" against non-believers. You say you have access to absolute truth in the Bible? Then why do Christians disagree among themselves about the absolute truth? What good is absolute truth if there are various versions of it? Sounds a lot like relativism to me, even on the Christian side of the equation. Thus, I would have taken Walton's case a step farther. Almost every opinion we have about God is a mixture of truth and error. If we think ourselves 100% correct in our opinions, we are 100% wrong about that belief.
I like Pascal's angle on it:
"Let us then take our compass; we are something, and we are not everything. The nature of our existence hides from us the knowledge of first beginnings which are born of the Nothing; and the littleness of our being conceals from us the sight of the Infinite. Our intellect holds the same position in the world of thought as our body occupies in the expanse of nature.
"Limited as we are in every way, this state which holds the mean between two extremes is present in all our impotence. Our senses perceive no extreme. Too much sound deafens us; too much light dazzles us; too great distance or proximity hinders our view. Too great length and too great brevity of discourse tend to obscurity; too much truth is paralysing. ... Extreme youth and extreme age hinder the mind, as also too much and too little education. In short, extremes are for us as though they were not, and we are not within their notice. They escape us, or we them.
"This is our true state; this is what makes us incapable of certain knowledge and of absolute ignorance. We sail within a vast sphere, ever drifting in uncertainty, driven from end to end. When we think to attach ourselves to any point and to fasten to it, it wavers and leaves us; and if we follow it, it eludes our grasp, slips past us, and vanishes for ever. Nothing stays for us. This is our natural condition, and yet most contrary to our inclination; we burn with desire to find solid ground and an ultimate sure foundation whereon to build a tower reaching to the Infinite. But our whole groundwork cracks, and the earth opens to abysses.
"Let us therefore not look for certainty and stability. Our reason is always deceived by fickle shadows; nothing can fix the finite between the two Infinites, which both enclose and fly from it."