There's nothing like a good game of "spot the similarities":
Yup, the cave and gallery segments are from SoTN.
The castle stone tiles heavily resemble those used in CotM. (0:51)
The "Merchant Crow" mimics the Master Librarian: their rooms are identical up to furniture placement. (1:12) And Lunais gets a fairy!
The sword ability harkens back to OoE. (0:43)
Jumping bone pillars (0:45) Skeleton Gunmen (0:51) Maneaters (1:17) and of course a cloud from Mario.
And yes, those little damage numbers should remind you of something.
They showed that to the public, with the goal to make money. Being placeholder is not an excuse for that. It's the very core of what intellectual property rights are designed to protect against.
Regardless, it'll be crime if this game doesn't get funded -- clone or no clone. Considering what Konami's actually been doing with its intellectual property, intellectual rights are the least of my worries. Besides, there just aren't enough Metroidvanias out there for my taste.