Difference in level reported by Match Loudness and Amplitude Statistics

[Peakoverload]

I normally use a different DAW and so am not too familiar with Audition but a client rejected a file saying it was too low in level and showed a screen shot from Audition to illustrate it.

When I playthis file in any other DAW (Reaper, ProTools, Logic) and run it through an RMS meter, I get the same reading within 0.2dB of each other that being -20dB RMS-I

However, the screen shot the client sent us from Audition showed that it was reading -23dB Total RMS in Match Loudness.

I've opened the file in my copy of Audition CC and if I load it into Match Loudness it shows as being -23dB. However, if I scan the file in Amplitude Statistics, it says the Total RMS Amplitude is -20dB.

Why the difference and which is correct?
I was wondering if the fact that it is exactly a 3dB difference was something to do with Pan Law as the file in question is Mono single channel and wondered if one was processing it as Dual Mono or Stereo and hence 3dB difference but I can't find anything about how Match Level analyses the file in the first place.

[SteveG_AudioMasters_]

First thing I'd want to know is why your client is trying to use a tool intended for a different purpose to assess your file anyway! All those other DAWs - and Amplitude Statistics - are correct. So is your file. Guess what isn't...? Match Loudness isn't a measuring tool to use for that purpose!

[Peakoverload]

Oh I completely agree. The problem is I'm trying to convince the client that they are doing it wrong and their response is "We've always done it this way and if it shows that level is too low in Match Loudness, we know it will be rejected when we upload it to the portal".
I think they are talking out of their you know what, and if I could explain to them in a way they would understand what Match Loudness is doing, and therefore, why it is wrong, and that the files we send them are exactly what they asked for it would save a lot of hassle. To be fair, we've worked with this client for years and have never had an issue before but they've rejected this file 3x times now, even though we keep increasing the level each time (even though we know that this is then making it too high in level).

[SteveG_AudioMasters_]

Try suggesting to them that Match Loudness is an adjustment tool, not a measurement tool, and that using it at all may be damaging the file! (That's unlikely to be the case, but what the heck...)