``reset`` is meant to reset the driver. It is used in the Behat MinkExtension to isolate scenarios cheaply for instance (with a tag to provide real isolation through stopping the driver). ```reset`` is not only meant to delete cookies. It is meant to reset the state of the driver. and these forms values are part of the state.
Visiting a page already resets them, so it should not be a big issue if reset does not clear them, but it could create issues in edge cases