Mail system should not be reset if SMTP on/off is overridden

In the settings.php for my local environment, I am overriding the SMTP settings to ensure that it is "on" by default:

$config['smtp.settings']['smtp_on'] = TRUE;

I also have the system mail set to "SMTPMailSystem" by default. However, if I got to the SMTP configuration page and save the settings, then the system resets my mail interface to "php_mail". The reason why is that the code in the submit handler for the form is checking the value of "smtp_on" from the editable config, not the overridden config. So it treats SMTP as disabled and thus resets my system mail to php_mail.