PDF changing upon opening in Photoshop!

It's well known that Illustrator ignores edits to a PDF, because the PDF also contains the original Illustrator file. It's much less well known (indeed, I didn't know) that Photoshop does the same; this PDF has the original PSD embedded in it, and this is what Photoshop will prefer to open. That way you get back all layers and other things.   This can be turned off by turning off the option "Preserve Photoshop Editing Capabilities" when saving the PDF. No such option on open. This is really quite an unusual workflow, which is why I think this problem (or valuable feature, depending on your point of view) is little known.

Here's a screen grab. The PDF on the left and PSD on the right. On further inspection, it appears that the file is reverting to a previous version! The logo on the top left tipped me off when it first happened! You can see it's not only a font change but a text change too! Both of the files are downloaded on my computer, so it's not grabbing from the cloud or anything. You can see the text changes and images. It's very strange!