ButtonGroup does not work inside of TabGroup

[Sam Groves]

The ButtonGroupAttribute does not work when used inside of a TabGroup.

OS: Windows 10
Unity: 2017.4.24f1
EditorOnly: false

This code:

Produces this:

A working ButtonGroup above the TabGroup and a broken ButtonGroup inside the TabGroup.

[Sam Groves]

Error with code.

Documentation not the clearest on how to use groups within groups.