Custom social connection with Instagram

The docs are confusing. I understand I need to create a new custom connection but this part from the docs doesn’t make sense for me:

Click the slider next to the social provider(s) you want to set up. The slider will turn from grey to green, indicating that a connection to that provider exists.

Why do I need to click a social provider to set up a new custom connection if my connection is custom. Because if it is a custom connection than I do not need to choose a social provider from a pre-selection.