Availability Groups don't let you select if needed times

[Gryphscribe]

I was filling out my schedule for an availability group, and wanted to use the "if needed" category to identify when I would be available in-person or online. However, I found I was not able to swap to input the "if needed" category, despite it displaying in the legend (picture below). Is there any reason this feature isn't available in Availability Groups? If it can't be added maybe the option should be removed from the legend, but ideally it would become an option.

Availability Group:

Event: