It's quite a coincidence, but I just read the following a few minutes earlier:
"It is important to bear in mind that whatsoever things were written aforetime, were written for our learning. They were not written for those who lived at the time. The things recorded happened to them as examples, but the record of them is for us. Therefore we go back to these things and take them up as types. We get now the anti-type, that is the reality. We get a great deal of typical teaching in the Old Testament. We often find in the Old Testament the detail of things; in the New we have the principles and facts. In the Old Testament you get the sacrifice of Christ in detail; in the New, the fact."*
If we regard the Old Testament as either not inspired, only partially inspired, or allegorical in any way, we lose out on this wealth of typical teaching, "the detail of things". These aren't insignificant details either, these are things concerning the Lord Jesus Himself. It should be noted as well that an allegory is not a type.
* 'Readings and Addresses in U.S.A. and Canada with F.E.R. 1898, page 15: 'Provision for the Wilderness - Priesthood and the Water of Purification' (Quebec, Tuesday Evening, October 4, 1898)