[just_for_you]

To my knowledge, I see most JPEG images encode their height in an "APP1" EXIF segment, and in their SOF1 segment (which is basically just a basic-info segment for the core JPEG bitstream). It's also possible to store the size in an APP1 XMP section, but that's mostly non-essential metadata for interchange purposes, and I usually don't see the size duplicated there for JPEGs anyway (PNG does though, if it has an XMP chunk).

It's possible that some of the other officially-defined segments (see https://exiftool.org/TagNames/JPEG.html) might also contain duplicate info, but then that'd be specific to the app that uses it, not for general-purpose use.

Storing the size in easily-parseable EXIF metadata and then once again in the JPEG bitstream seems pretty reasonable to me. Not to mention if you run a metadata/EXIF stripper on a JPEG file, then you remove all duplicate info and the only remaining image-dimensions will be stored in the JPEG bitstream anyway.