Steps to reproduce:

1. Open attached project
2. Open scene "Main" and run it
3. Notice console: first "True" is printed when button is parented by Interactable canvas group, second "True" is printed after button is moved to be non-directly (CanvasGroup>Container>Button) parented by non-interactable canvas group.

You can also inspect this issue by enabling Debug Inspector and observing that "Groups Allow Interaction" is true.

Note: If button is re-parented to be a direct child (CanvasGroup>Button) of non-interactable canvas group then IsInteractable returns False as it should.

Workaround: Override Button and add following method to the script:
protected override void OnTransformParentChanged()
{
OnCanvasGroupChanged();
base.OnTransformParentChanged();
}

Reproduced with: 5.3.1f1, 5.3.7f1, 5.4.2p4, 5.5.0b11, 5.6.0a3