First, thank you for the compliment.
Second, what you have discovered is that not all microphones are alike even if they produce good quality/clear dictation output.
For example, I use the SpeechWare 6-in-1 and the SpeechMatic USB MultiAdapter & USB TravelMike (two of them) on three of my four systems. The fourth system is running Dragon Medical Practice Edition 2.3.1 using the Samson Airline 77 Wireless microphone. As good as the Samson Airline 77 Wireless microphone is, the proper setting for the VC microphone is different that it is for the SpeechWare microphones. Because the SpeechWare microphones have the built-in auto gain control, the confidence level for these microphones has to be set significantly higher than for the Samson Airline 77 Wireless microphone.
My point is simply this the settings that work best for each user with regard to setting up the VC microphone is highly dependent upon the type of microphone you're using as well as the specifics relative to the output signal volume and quality produced by each.
In short, what you point out is a perfect example of the above.