Sign with digital ID on macOS Customize signature appearance cannot choose image files only PDFs

When I attempt to digitally sign a document by clicking on the signature field, it brings up "Sign with a Digital ID" dialog box.
After creating a new entry in the keychain it gives me the options to choose how the signature should appear on the document:
- Text

- Draw

- Image

- None
I would like to use my signature scan that I previously uploaded to my computer.

So I choose "Image" > "Browse"

It brings up the standard Finder to select my image file.

Result:
Only PDF files are valid to select. When I hit options at the bottom, the "Show" dropdown only allows Acrobat PDF Files to be selected.

Expected:

I can choose any valid image format (PNG, JPG etc)

Are there any work-arounds to this? Or some hidden configuration setting? Or is this just a bug?

On the off chance it would work, I tried renaming the PNG => PDF.  *FAILED*
I also tried opening the PNG in "preview" and exporting to PDF. This half worked, however the signature is rotated incorrectly, and cannot be adjusted, so I cannot use that either.