Clarify that ssl.OP_ALL can be different from OpenSSL's SSL_OP_ALL.
diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst
index 0bd54c7..8cd07d7 100644
--- a/Doc/library/ssl.rst
+++ b/Doc/library/ssl.rst
@@ -316,7 +316,8 @@
 .. data:: OP_ALL
 
    Enables workarounds for various bugs present in other SSL implementations.
-   This option is set by default.
+   This option is set by default.  It does not necessarily set the same
+   flags as OpenSSL's ``SSL_OP_ALL`` constant.
 
    .. versionadded:: 3.2