“ sophisticated tradecraft “ lol what?
It’s generally illegal in most countries to use another country’s passport within the country your passport is from. You can’t have a German and Argentinian passport and enter Germany with the German passport and leave with the Argentinian one. Nor can you leave Germany with just the Argentinian one. You can go to other Schengen countries, but you can't leave the Schengen region ("since is your entrance stamp?")