Yes possible with anything. Instead of sending the content of the message they send an expiring link which is transparent when viewed in GMail.
You can save the message contents with effort, that's not really the threat model this is feature is addressing. But neither POP nor OfflineIMAP will help you by default.
You can save the message contents with effort, that's not really the threat model this is feature is addressing. But neither POP nor OfflineIMAP will help you by default.