The "Crown" Chakra is the downward pointing energy source that exists at the the top of your head. Touch the top of your head and visualize a thousand-spoked lotus pointing down into your body. This is your crown chakra.
In Sanskrit the Mind of God is referred to as SahasrAra (सहस्रार) chakra. SahasrAra literally means thousand-spoked lotus pointing down on your brain. When considered as such, referring to the chakra as a "crown" seems inappropriate. Indeed, I would suggest that referring to the sahasrAra chakra as the "crown" is an appropriation and corruption of the concept by western spiritual elites. Since a "crown" is something only a few of the worthy/chosen/strong/evolved ever get to wear, presumably an activated crown chakra is only something a few are able to achieve.
In order to erase the hierarchical implications inherent in the naming of sahasrAra chakra as a crown, the LP uses the noun Mind of God to refer, in English, to the sahasrAra chakra.