Hi, @Andrew Robinson Welcome to Microsoft Q&A thanks for posting your question
When you select "default," it signifies your intention to follow the version recommended by Azure Cache for Redis. Currently, this "default" setting equates to TLS 1.2, as it has served as the standard for the past 2-3 years.
This is a good callout, we will update our docs and try to make it more clear on the portal that "default" is TLS 1.2 currently
Regards
Geetha