There is no installcheck element in the bootstrapper package manifest shipped with Visual C++. Guess Microsoft wants to always install if you set it as a prerequisite.
Of course you can still call MsiQueryProductState to check if the VC redist package is installed via MSI, The package code can be found by running
wmic product getat command line, or if you are already at wmic:root\cli, run
product where "Caption like '%C++ 2012%'"
