Uppercase metadata keys do not allow automatic sorting in Page Properties Report

Steps to reproduce:
1. Add the Page Properties macro to your page and specify a label (for example, Status).
2. Add a two column table in the body of the macro placeholder for your metadata keys and values. Use a key with at least one uppercase letter, e.g., Key. Enter an arbitrary value.
3. Repeat this process to add the Page Properties macro to other pages.
Create a new page to contain your report (for example, Status Report).
4. Add the Page Properties Report macro and specify the same label (for example, Status). Specify the 'Sort By' property of the macro to chosen key, e.g., Key.
5. View your new status report page.

Expected result: The report is sorted by the column Key.

Actual result: The report is sorted by the last-modified date, as specified in the default behaviour.

Workaround: use lowercase keys.