Stealth doesn't work like you think it does, stealth doesn't makes aircraft invisible to radar, it makes them practically invisible to radar targeting systems as in it lowers and changes their RCS enough to not be considered an aircraft by the system that tracks them.

And while their stealth tech might be much more advanced than ours, and provide true EMF absorption (as long as they have some sort of internal heatsinks because you can't break laws of thermodynamics) that tech wouldn't do you any good when you enter the earth's atmosphere you'll be lit like a christmas tree.