Forum v2 create mongodb indexes?

The init job calls the following line:

./manage.py lms forum_create_mongodb_indexes

Is this because of

Even if the forum v2 toggle is not enabled, edx-platform will make a call to the forum v2 API in some edge cases. That's because edx-platform needs to determine whether it should use forum v2 or cs_comments_service, based on the value of some course waffle flag. In order to access the course wafffle flag, we need to determine the course ID of the current HTTP request. In some requests, the course ID is not available: only the thread ID or the comment ID is. Thus, edx-platform needs to fetch the course ID that is associated to the thread or comment. That information is stored either in MySQL or in MongoDB. Thus, edx-platform needs to call the forum v2 API.

As a consequence, the forum v2 app needs to have accurate MongoDB configuration settings even if you don't use forum v2. In a Tutor installation, these settings are set to the right values. In other environments, the following Django settings must be set:
...

Me no comprendo. I thought v2 was mysql. If I do use v2, I can understand I might need a mongodb for “legacy” reasons. So I also need to create the indexes? Is that where the code goes to look whether it’s v1/v2?

Thanks!