[danwills]

Sounds like it should be possible if you can terminate the transfer of the file early:

> libjpeg has some interesting features as well. Rather than decoding an entire full-resolution JPEG and then scaling it down, for instance (a common use case when generating thumbnails), you may set it up when decoding so that it will simply do the reduction for you while decoding. This takes less time and uses less memory compared with getting the full decompressed version and resampling afterward.

[makapuf]

The paragraph you quoted simply means that the decompression library is able to decompress to a smaller size raw image, and says nothing about jpeg file format.