I'm pretty sure you're right yeah, I've dabbled in building my own 2D HTML/JavaScript based engines and think you're spot on with the movement. From what I can see he's fading out and in the old and new image but with the zoom used it actually feels like you're moving.
I've also seen some videos on how Doom, Wolfenstein and later 2D simulated 3D engines work and this looks exactly like that, just prettier.
But Sébastien was lead dev on Dead Cells, so I bet he knows some magic. He has a github, might be interesting to crawl through that: https://github.com/sbenard