The VERIFY_INTERFACE_HEADER_SETS must not always enabled?

Beman Libraries
1 
set_target_properties(beman.exemplar PROPERTIES VERIFY_INTERFACE_HEADER_SETS ON)

should be

set_target_properties(beman.exemplar PROPERTIES VERIFY_INTERFACE_HEADER_SETS ${PROJECT_IS_TOP_LEVEL})

and it should not be enabled if CXX_MODULES are compiled?

if(BOOST_USE_MODULES)

    # Ensure CMAKE_CXX_STANDARD is set for module detection
    if(NOT DEFINED CMAKE_CXX_STANDARD)
        set(CMAKE_CXX_STANDARD 20)
    endif()

    add_library(boost_any)

    target_sources(
        boost_any
        PUBLIC
            FILE_SET modules_public
                TYPE CXX_MODULES
                FILES modules/boost_any.cppm
    )

    # Require C++20 for modules
    target_compile_features(boost_any PUBLIC cxx_std_${CMAKE_CXX_STANDARD})

    # Define macro indicating modules usage
    target_compile_definitions(boost_any PUBLIC BOOST_USE_MODULES)

    # Check if import std; is available for the current standard
    if(${CMAKE_CXX_STANDARD} IN_LIST CMAKE_CXX_COMPILER_IMPORT_STD)
        target_compile_definitions(boost_any PUBLIC BOOST_ANY_USE_STD_MODULE)
        set_property(TARGET boost_any CXX_MODULE_STD ON)
        message(STATUS "Boost.Any: Using `import std;`")
    else()
        message(WARNING "Boost.Any: `import std;` is not available for C++${CMAKE_CXX_STANDARD}")
    endif()

    set(__scope PUBLIC)

else()

    # Modules disabled -> INTERFACE library
    add_library(boost_any INTERFACE)

    # If modules are disabled, require C++17 for headers
    target_compile_features(boost_any INTERFACE cxx_std_17)

    # Verify interface headers only at top level
    if(PROJECT_IS_TOP_LEVEL)
        set(CMAKE_VERIFY_INTERFACE_HEADER_SETS ON)
    endif()

    set(__scope INTERFACE)

endif()