CMake: Failed to set iOS deployment target from command line

I use this command line to generate Xcode project for iOS

    cmake -GXcode \
        -DENABLE_TESTS=ON \
        -DCMAKE_BUILD_TYPE=Release \
        -DCMAKE_TOOLCHAIN_FILE="$ProjDir"/cmake/ios.cmake \
        -DIOS_PLATFORM=OS64 \
        -DIOS_DEPLOYMENT_TARGET=9.0 \
        "$ProjDir"

I can see in the CMake output the version has been set

....

-- Using a data_ptr size of 8
-- Building for minimum iOS version: 9.0 (SDK version: 14.0)
-- Version flags set to: -miphoneos-version-min=9.0
-- Enabling bitcode support.

....

However, the generated Xcode project still uses default target, e.g., iOS 14 with Xcode 12.

What's wrong?