Don't forget that the only way to realize 130db dynamic range in a PCM recording is to run 24 bit at almost full digital scale. If your recording peaks are just reaching -8, then you are only recording at 16 bit depth. You'll still get 96 db of dynamic range which is more than most recording situations have anyway. Just don't put too much weight on 130 db analog dynamic range when running full digital scale is the only way to actually get it.
I've been trying to think through the real world consequences of noise and recording level, so this is a bit off track from what I've been contemplating. But I think this is off a bit. True, in theory for PCM each bit can capture 6db of dynamic range. So a theoretically perfect 16 bit recorder can capture a dynamic range of 96db, and a 24 bit recorder can capture 144db of dynamic range. To capture a dynamic range of 130db (or up to 132db), you only need 22 bits. But if you capture at -8dbFS, it is only a hit of 2 bits. But even at 22-bits, 132db of dynamic range can be captured, which is more than the 130db dynamic range of the recorder in your example.
I don't know how recording at -8dbFS in a real world recorder plays out. Recording at -8dbFS effectively makes the recorder a 22-bit recorder, which should be able to capture 132db of dynamic range. I don't believe that a real-world recorder that provides 130db of dynamic range would be reduced to 122db of dynamic range when recording at -8dbFS since it isn't necessarily a linear thing (e.g., there is an amount of self-noise within the ADC). But even if that were the case, 122db of dynamic range would require 21 bits of information. I'm not sure why you assume this situation means you're only recording at 16 bits. Seems like you're treating the -8dbFS as a shift of 8 recording bits (24 to 16), but I'm not getting why that is.
BTW, the MixPre-6's ADC has a dynamic range of 120db according to their specs, not 130db.