Correct comments on the Core ML wheel library

CMakeLists.txt

@@ -1421,9 +1421,10 @@ if(EXECUTORCH_BUILD_PYBIND)
   # --no-as-needed around its own file to every consumer, so the CUDA and
   # OpenVINO backends are covered by that and are deliberately absent here. That
   # export is emitted only for NOT APPLE, so it does nothing for an Apple-only
-  # delegate like Core ML; those are covered instead by Mach-O, which keeps a
-  # named dylib's namespace-scope initializers without an --as-needed
-  # equivalent.
+  # delegate like Core ML; that dylib is instead kept because it is named
+  # directly on the link line, which retains its namespace-scope initializers
+  # without an --as-needed equivalent. Only -dead_strip_dylibs would drop it,
+  # and nothing here passes that.
   foreach(_retained_component optimized_native_cpu_ops_lib xnnpack_backend
                               extension_threadpool etdump
   )

backends/apple/coreml/CMakeLists.txt

@@ -199,7 +199,10 @@ if(APPLE)
   # link it, and so the Python extension links it dynamically instead of
   # absorbing its code. Keyed on EXECUTORCH_BUILD_SHARED rather than
   # BUILD_SHARED_LIBS, the same way the other shipped delegates decide this, so
-  # the wheel controls it independently of the generic CMake switch.
+  # the wheel controls it independently of the generic CMake switch. Shipping it
+  # shared means a duplicate-symbol conflict would surface at load time rather
+  # than at static-link time; the process must hold exactly one copy of the
+  # delegate, which the single shipped library and the dynamic link preserve.
   if(EXECUTORCH_BUILD_SHARED)
     set(_coreml_backend_library_type SHARED)
   else()
@@ -270,7 +273,9 @@ if(APPLE)
     # the delegate references the helpers it uses, so ordinary resolution pulls
     # exactly those objects. Neither helper registers anything from an
     # unreferenced namespace-scope initializer, which is the only thing
-    # force_load would add here.
+    # force_load would add here. Private also keeps the helpers' include
+    # directories out of this library's export interface, which is intended: a
+    # wheel consumer links the bundled delegate and never names the helpers.
     target_link_libraries(
       coremldelegate PRIVATE coreml_util coreml_inmemoryfs executorch_shared
     )