I used my current development version (7.47 beta), but nothing has changed in the ORF code since 7.45.
The commands I used were:
exiftool -thumbnailimage -b FILE.orf > out.jpg
exiftool -datetimeoriginal -createdate -a -G1 FILE.orf
I also took a look at the file structure with
exiftool -htmldump FILE.orf > out.html
and I didn't see any unextracted JPEG images hiding anywhere in the file.