Yes, it's been like that since at least OpenMPT 1.21.
Either way - hex-editing files out of curiosity is fine, of course, but pretty please - don't try to create and release new SoundTracker modules in 2020. SoundTracker is not just ProTracker with 16 less samples and shorter samples. The document you found grossly simplifies the
minute differences between various SoundTracker versions, and every newly created song can potentially break the heuristics various players use to determine which exact SoundTracker clone was used to create such a file.
It's better if we leave this format in its grave and don't make the situation even more complicated than it already is. Just look at those tables of different effect interpretations (e.g. Dxx sometimes is a volume slide, and sometimes a pattern break) to get an idea how messed up the situation already is. Among other things, this is why OpenMPT (or any other tracker, for that matter) doesn't simply resort to writing your MODs as SoundTracker files if they happen to use less than 16 samples.