Well OK, it's the blue tinged sky that bothers me most. That's a rather specific atmospheric effect. It doesn't exclude day and night (which is simply a planet's rotation towards a star). WFC indicated they had day and night (including the lighting effects), but not as much an atmosphere that caused sky coloration (our sky is blue because of the nitrogen/oxygen mixture mostly). I'd find it odd if Cybertron suddenly had the same atmosphere as Earth.
"Iacon Destroyed" showed clouds in the backdrop at the very least, so OK that might indicate a atmosphere to some extent (could be gas clouds, but like the cartoons, it at least allows/implies oxidation/fire), but so far Cybertron has mostly been portrayed as a planet without a (colored) atmosphere.
Nitpicking I know, but to a certain extent the slugs of WFC were already... 'problematic' in my mind.