Are you missing something? Do you find it difficult to look at invoices of recently received approval books, lists with subjects all mixed together? In the absence of review shelves of approval books, and the merging of major vendors, do you worry about whether the library is still receiving the quality of the past? It's not difficult, really. You can sort by Topic, Dewey or LC.
Here's an easy (and at least partial) solution to the problem:
These lists are compiled by YPB subject specialists with books-in-hand. "The titles selected are carefully screened to identify major titles that will stand the test of time, which would be considered standard (core) works in any good undergraduate collection….each profiler [is] responsible for specific topics, corresponding with the subjects each bibliographer focused on in their academic career."