doc: clarify writable.cork method

doc/api/stream.md

@@ -358,9 +358,9 @@ The `writable.cork()` method forces all written data to be buffered in memory.
 The buffered data will be flushed when either the [`stream.uncork()`][] or
 [`stream.end()`][stream-end] methods are called.
 
-The primary intent of `writable.cork()` is to avoid a situation where writing
-many small chunks of data to a stream do not cause a backup in the internal
-buffer that would have an adverse impact on performance. In such situations,
+The primary intent of `writable.cork()` is to accommodate a situation in which
+it is more performant to write several small chunks to the internal buffer rather
+than drain them immediately to the underlying destination. In such situations,
 implementations that implement the `writable._writev()` method can perform
 buffered writes in a more optimized manner.