It’s still a JPEG, not a true JPEG/TIFF hybrid. What’s likely inflating the file is Photoshop metadata—especially large Document Ancestors entries stored in the EXIF/APP segments. That extra metadata can add megabytes, so changing JPEG quality may have little effect if the metadata is the main problem.

A few key points:

• JPEG files may be stored in EXIF form rather than JFIF, which can confuse some apps’ file info.
• The image data itself is still normal JPEG-compressed image data.
• Removing metadata can dramatically reduce file size.

How to save a more typical JPEG:

• In Photoshop, use Save for Web / Export As if available, since these typically strip unnecessary metadata.
• Or remove metadata with a tool such as ExifTool before or after saving.
• A normal Save As > JPEG may preserve Photoshop metadata, including Document Ancestors.

So the fix is not lowering quality further—it’s exporting without the bloated metadata.