I think the point is being missed.
1. Self Enrolment has the ability to send a welcome message, if the student self enrolled this is redundant in our opinion.
2. With a Cohort Sync or when Importing users using a file, or with Manual Enrol, NO WELCOME MESSAGE is sent.
The logic seems backwards.
One forum member even suggested that students use their dashboard and voila no problems, except for as an example is HR needs to assign training to staff that are not using Moodle on a daily basis. In such an environment the users need to be informed that they have been enrolled in a new course yet there is NO METHOD THAT AUTOMATES this.
Yes you can send an email to selected users manually, however this should be unnecessary IF moodle's enrolment plugins weren't half baked.
There are countless threads going back 6 years asking for consistency with the Enrolment plugins yet here we are.
There is a plugin that MIGHT resolve this however it has not been updated since Moodle 3.3 and the project appears to be dead.
Would love to see "Send a welcome message on enrolment" at the Course level rather than depending on the method used to enroll.