From that article, and as you partly quoted...:
"The previous 'triple-punishment' rule required a red card - and therefore a suspension - as well as the award of a penalty under those circumstances...
...But deliberate fouls will still incur a red card.
Those include holding, pulling or pushing, not playing the ball, serious foul play, violent conduct or deliberate handball in order to deny a goalscoring opportunity."
In which case:
a] This was outside the box, thus not a penalty, and thus not within the "triple-punishment" area which (should) be relaxed.
b] It's a deliberate handball which stops a goalscoring opportunity.
I can't see why it wasn't a red. I'm thankful, but don't get it at all.