I just downloaded the latest 7.5 (licensed, advanced, so not a trial version), and the font size doesn't work. In fact, the official documentation example shown here: https://www.phpdocx.com/api-documentation/layout-and-general/create-Word-custom-paragraph-style-with-PHP doesn't work. The font size is set to 26, but the screenshot clearly shows a much smaller font.
Executing the example found at examples/LayoutAndGeneral/createParagraphStyle/sample_2.php doesn't work either. The font will always remain at the default size.