CMAKE_INSTALL_PREFIX vs installDir in a CMake configure preset

Usage
1

I defined a CMake configure preset like this:

{
  "configurePresets": [
    {
      "name": "base",
      "displayName": "Base configuration",
      "cacheVariables": {
        "CMAKE_INSTALL_PREFIX": "install"
      },
      "binaryDir": "build",
      "installDir": "install"
    },
  ]
}

I tried, and it turns out that for providing the installation directory, it is sufficient to give either CMAKE_INSTALL_PREFIX or installDir. Are they interchangeable or there is a difference between the two?

2

The presets documentation for installDir provides the answer:

An optional string representing the path to the installation directory, which will be used as the CMAKE_INSTALL_PREFIX variable.

3

Yes, I read the documentation, but I did not understand the consequences of setting directly CMAKE_INSTALL_PREFIX in cacheVariables instead of setting installDir, which implicitly populates CMAKE_INSTALL_PREFIX. In other words, what is the role of installDir if I can anyway set it in CMAKE_INSTALL_PREFIX?