Dispatchers.IO doc clarification (#3236)

Addresses #3234

Author: qwwdfsad

kotlinx-coroutines-core/jvm/src/Dispatchers.kt

@@ -125,8 +125,9 @@ public actual object Dispatchers {
      *
      * This dispatcher and its views share threads with the [Default][Dispatchers.Default] dispatcher, so using
      * `withContext(Dispatchers.IO) { ... }` when already running on the [Default][Dispatchers.Default]
-     * dispatcher does not lead to an actual switching to another thread — typically execution
-     * continues in the same thread.
+     * dispatcher typically does not lead to an actual switching to another thread. In such scenarios,
+     * the underlying implementation attempts to keep the execution on the same thread on a best-effort basis.
+     *
      * As a result of thread sharing, more than 64 (default parallelism) threads can be created (but not used)
      * during operations over IO dispatcher.
      */