They got it mixed up, 921 is the one on the left.
I should add, the 921 on the left is the CBC configuration, so same sort of thing as Falcon Heavy, Delta IV Heavy etc. It's intended for launching big stuff like moon surface station parts to deep space.
The plan also calls for 921 core to be used on its own for LEO heavy lift missions. The core is 5m diameter so big payloads like CSS parts would fit right on top. It's also intended to be man-rated as you can tell from the LES tower. 921 CBC configuration would have something like 70 tons to LEO capacity. 921 core only would have less payload to LEO than LM-5.
First stage (or each booster in the CBC version) is seven YF-100K engine, second stage is two YF-100M, third stage is three YF-75D. All are existing engines so the rocket is just a new way to put them together.
Due to the clustering of engines in the first stage it's suspected that the intention is for first stage to be recovered ala Falcon Heavy. Long March 8R is also intended for recovery and uses the same engines (four of them) in its recoverable stage.
