Please explain how folks in oppressive countries can get pardons again?

Now Biden is telling folks from four countries with questionable governments that if they show up at the border they will be sent home immediately. But if they go home and apply for asylum from their home country, they will be pardoned and allowed in.

So if you are fleeing from Cuba, Nicaragua, or Venezuela just go back and you'll be pardoned. So Mexico has also agreed to House 30,000 a month of the asylum seekers.

Now Biden can send them back, but not the millions of the folks from other countries?