I presume it is similar to locals where you scan your card going in and out and then the gate opens, but what is more interesting to me is the this:

And the United MileagePlus® Club Card will give you Platinum status if you link it with your Hyatt account. If you hold one of these cards, you’re eligible for an M life status match and free valet parking!

In a nutshell if you have the United credit card you can get Hyatt Platinum status and by that you can status match to M Life Gold and get free parking. And you still get United miles.