He [William of Conches] is an interesting character for Creationists to take stock of. Here is another quote attributed to him (back in the 12th century no less!) as he even then rejected literalistic readings of Genesis.
"The authors of Truth are silent on matters of natural philosophy, not because these matters are against the faith, but because they have little to do with the upholding of such faith, which is what those authors were concerned with."
M-D. Chenu. Nature, Man and Society in the Twelfth Century: Essays on New Theological Perspectives in the Latin West, Chicago University Press, 1968 (as cited by Hannam in "God's Philosophers" p. 63).
Thanks for bringing him up here. I wish we knew more about him.