Citing Data That Was Compiled From Many Sources and Then Summarized? (Updated) The Problem

The author of the dissertation (PhD) collected publicly available raw data from the websites of over 40 universities. The data itself spanned 40 years. After compiling the data into a spreadsheet, the author diced it and sliced it to create well-summarized figures and tables. For example, one figure is a graph of the number of hires over time; a potential figure is a map showing where the hires occurred. And a table shows the hires by name, year, and location. (Anonymity at this point is not an issue. All data are publicly available.)

The manuscript needs to comply with APA 7 standards. The APA 7, 6, and 5 manuals go into great detail with examples about meta analysis for experimental purposes, but nothing I read "clicked" for how to deal with this situation.

Based on other posts at this site, the author's summary is a type of meta review (not a deep-dive analysis as described by the APA standards). The purpose of the data is only to present the situation as it has been over time to put the background for a qualitative case study into context. Maybe you'd call it a demographics meta review or demographic meta report?

Potential Solution

Given that the guidance in the APA manual did not seem to fit this situation, my inclination was to suggest the following: 


an appendix that lists the university names, locations, and URLs, with an explanation that the data shown in the tables and figures were compiled from data at the university web sites
figure notes and table notes that refer to the appendix.
a entry in the References for the manuscript author (i.e., the author citing himself because he compiled the data in unique ways).


The Question


Would the above potential solution be APA compliant?
If not, what is the APA solution?


Whatever the answer, it would be helpful to have a pointer to the page or pages in an APA manual (version 7, 6, or even 5) that support the answer.
What you have described is your data collection procedure, so I would put it in that subsection (within a methodology section). Describe the procedure of creating the combined dataset clearly, in a way that another researcher would be able to reproduce it.
There you can refer to all your sources, directly in the text, even though it is extensive. Then you should add the reference for each published dataset they've used to construct the large dataset in the reference list (which should be in the APA-handbook, see https://apastyle.apa.org/style-grammar-guidelines/references/examples/data-set-references). I would not reference in the form of a self-reference to what is basically the current work.