As I tried to explain before, bigbluebuttonbn_sendnotifications_enabled has nothing to do with the Recording Ready notification. You should look for another one that is bigbluebuttonbn_recordingready_enabled.
I am still confused on why is that feature working for you at all, but it definitely has to do with your settings.
1st question. What BigBlueButton server
are you using?, your own or someone is hosting for you? Because if that was the case you can shutdown that capability enterly in that BBB server by renaming the script
sudo mv /usr/local/bigbluebutton/core/scripts/post_publish_recording_ready_callback.rb /usr/local/bigbluebutton/core/scripts/post_publish_recording_ready_callback.rb.disabled
2nd question. Did you change anything in the config.php settings, either moodle/root/config.php or moodle/root/mod/bigbluebuttonbn/config.php? there are some settings you can alter there, so, one option is to make sure that this $CFG->bigbluebuttonbn['recordingready_enabled'] = 1; is not set to tru, and furthermore, set it to 0 as $CFG->bigbluebuttonbn['recordingready_enabled'] = 1;
That variable won't show up in the plugin settings because it was kind of experimental until BigBlueButton 2.2 was released. Before that this script was only part of Blindside Networks servers. But it is even enabled by default since the last fall.