Vale on/off comments do not work on titles in RST

This RST:

.. vale off

this text should be fine
------------------------

.. vale on

with a style that forbids the word "text", still generates an error:

 3:6  error  Use 'words' instead of 'text'  example-styles.example

In my understanding, no error should be raised in this case.

With the exact same setup, this file (correctly) does not generate an error.

.. vale off

this text should be fine

.. vale on

Tested with .vale.ini as:

[*.{md,rst,txt,json}]
BasedOnStyles = example-styles

and the only style in example-styles being:

extends: substitution
message: Use '%s' instead of '%s'
level: error
swap:
  text: words

Seen on Mac OS 11.2.1, vale 2.9.1 installed through homebrew. It's a bit too complicated (and I don't know Go) to debug further on my own.

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