The Ninja multiconfig example over in here: https://doc.qt.io/qtcreator/creator-build-settings-cmake-presets.html

Specifies the multi-config via:
"CMAKE_BUILD_TYPE": "Debug;Release",
However, this cmake variable is for single configurations.

It may be when the docs were put together cmake was more lenient, but configuring with cmake 4.0 will cause an error.

Multi-configuration generators should use: CMAKE_CONFIGURATION_TYPES.