It would be incorrect to assume too much about this level before watching, thinking that it is a full on Metroid game. Instead, it is just a little bundle of goodness, seeing Mario explore interconnected hallways and tunnels, looking for upgrades that will help him explore beyond barriers.
One complaint I already have about Super Mario Maker is being unable to turn off the time limit. That is something Nintendo should consider changing as it holds back the potential to create even larger levels. Other than that, I spot a few areas that could make the player genuinely “stuck,” impossible to proceed, which goes against the nature of Metroidvania. However, with a few tweaks, this is something that could be a huge hit.