Manufacturer's data doesn't work when you're using a third party or non-mass-market developer.
I haven't had a need to try this. I have a binder in the darkroom with printouts from the massive dev chart for each developer I use. It gets me close.
I agree that the MDC is a Godsend sometimes, but it ain't perfect either. At least not for me and Arista EDU/Foma 100 120 film. This method might have saved me a little time and material if it works. JohnW