Essentially I can find only one source online that uses this exact phrase in an educational context. (I won't give the URL for the source here lest your client find it in a search.) The source uses this and a similar phrase (search within the file for "いずれも") a total of 5 times, and although in 3 of those 5 instances it uses the phrase just as you give it, in the remaining 2 instances it instead uses "合否を付記する". Because in those 5 instances the sentence also varies between "いずれも可以上であれば" and "基準に達していれば", which are essentially synonyms, and "優劣を付記する" is found with both of these forms, I suspect that the document is also using "優劣を付記する" and "合否を付記する" as synonyms, and that the difference is only a result of sloppiness or inconsistency.

Literally, "優劣を付記する" would mean that they are ranking one person's test results against another person's, and I notice that the 3 instances where it is used are the only ones where the first of the 4 criteria, the written test, is indicated as only "if necessary". Nevertheless, because all of the sentences where "優劣を付記する" is used begin by discussing "...れば合格とする", I think that in these 3 sentences they are simply trying to say, "If you have a passing score in each part, then you will pass, [but if you have a failing score in one or more parts, then] we will take your overall score into account when deciding whether you passed or failed."