The airflow measurement is MAF only in blended mode as long as there are no transients. That's why this method works and why there is no need to waste time switching between them. If you're dubious, you can plot MAF, dynamic airflow and volumetric efficiency airflow in the scanner. At steady state, MAF and dynamic airflow are always right on top of each other even when GMVE is not disabled. And even if the GMVE is completely wrong. So long as you keep steady, airflow calculation from speed density is not used to determine fuel mass at all. It is however used to update the VE correction factor.
The patent is here with some block diagrams if you want to read about it: https://patents.google.com/patent/US20050060084A1/en
I know this is accurate because I designed software for GM and have seen all of the source code for this software :)