Does QuickTime 7.7 no longer support QTText descriptors?

Using QuickTime Pro 7.7.4 for Windows, I have been following various instructions found online for adding captions or subtitles to a video using a text file with QTText descriptors. I was having no luck getting most of the descriptors to work (font, style, left justification, drop shadow, etc.).The width and height of the text track were correct, and the time codes worked as they should. I was particularly confused by the font size; increasing it made no difference up to 24-point, and then the text suddenly jumped up to an enormous size.

I was thinking that the file must be formatted incorrectly, but after unintalling QuickTime and downgrading to 7.1.6, everything worked as it should.

Are there new text descriptors, or has support for this functionality been removed? I noticed that the list of descriptors on the Apple website is no longer present, only available in an archived version. I haven't tried this on a Mac; is this just a QuickTime for Windows issue?

Any insight would be greatly appreciated; thanks in advance!