Thanks! Great comment. I do not consider myself the authority on this, but here are my two cents. There is one person online I rely on for all things loudness standards and his name is Paul Figgiani from Produce New Media. Paul helped me with audio questions when I first started my podcast and I remember him posting a comment shortly after Apple published their Authoring Best Practices. It was my understanding that the main difference between the ITU -3 and ITU -4 was the verbiage and the measuring technique was different, but the differences in results were negligible. The ITU -3 (as in Audition) uses LUFS and ITU -4 LKFS. According to Paul, the terms are synonymous.
As for Apple recommending the same loudness for both stereo and mono: a stereo file at -16 LUFS is going to be perceptually the same as a mono file at -19 LUFS. While the numbers are different, they are the same to the ear.
In short, I do not think anything needs to change in how you use Match Loudness in Audition as the results will be the same. Will be interesting if they change to -4 verbiage.
Thanks again and Happy Holidays,