Here are the actual quotes from io9:
“I had this whole thing boarded where we’re where we see [Decepticon leader] Megatron and he comes in like Sauron, just blowing shit up and laying waste to everything,” Knight said. However, he then realized in this world, Megatron is currently frozen on Earth, as seen in 2007's Transformers, so that was out.
“So even though I really wanted to see G1 Megatron on the battlefield at the fall Cybertron, I couldn’t do it,” he said. “But I wanted to fit as much of this G1 stuff I loved in there, and so I put my favorite characters in. Obviously there are ones I wish I could put in there, and I would love to see an entire movie about the fall of Cybertron because I think it’s awesome, but just to be able to visit it for a moment, to see the Cybertron of my imaginations on the big screen, it was a real thrill.”