[api] State the destructor trade-off as a codebase rule, not a language guarantee

esphome/components/api/proto.h

@@ -739,9 +739,10 @@ class ProtoDecodableMessage : public ProtoMessage {
    * @return Number of times the field appears in the buffer
    */
   static uint32_t count_repeated_field(const uint8_t *buffer, size_t length, uint32_t target_field_id);
-  // No protected destructor here: without virtuals nothing can be deleted through this class, and the
-  // generated messages are aggregates whose sub message members are brace initialised, which needs an
-  // accessible destructor on the base temporary. ProtoMessage keeps its guard for the dump builds.
+  // The destructor stays accessible on purpose: the generated messages are aggregates that brace
+  // initialise sub message members, which copies a base temporary. That trades away the compile time
+  // guard against deleting through this type; messages are stack locals and never owned through a base
+  // pointer. ProtoMessage keeps its guard for the dump builds.
 };
 #ifndef HAS_PROTO_MESSAGE_DUMP
 // decode() passes decode_field explicitly, so nothing here may add a vtable