itch.io

Huh, Nevermind then. that is strange.  I don't know how I didn't see that anywhere. Well, I'm pretty sure it goes both ways then. 
So you can make a newer game retro, Or you could make an older game like... a year or 2 more recent I suppose. 

Pretty sure its just visual. I can't imagine they expect you to go that far out of your way to stay in theme. 

So Y'know, Dithering, Low poly models, Pixely textures, Bit crushed sound in some cases, That whole deal. 

Hope this helps! Good luck on the jam if You're participating!

The whole point is to take a newer game and port it to a classic console. I believe the line your referring to was when the Host of the jam was saying you need to follow the limitations of the console. (Which he means you SHOULDN'T make a 3D game and list it under a 2D console, The Atari being the example They used) Hope that helps! Good luck with the jam if You're participating!