Yes, that is what they're referring to. The technical details behind it are kind of cool. It's a "bug" of the JBIG2 compression algorithm. See 1, 2

[1] https://community.apryse.com/t/jbig2-compression-issue/1814

[2] https://en.wikipedia.org/wiki/JBIG2#Character_substitution_e...

All I see is 1, 1