I feel like you could have easily guessed that was the case from previous trailers and the fact that it uses the Horizon engine.
Either way, the gameplay loop is most likely not the same. DS looks more like traversal/ parcel management/ stealth for the real world, with stealth/ action for the upside-down realm. So the latter is probably more MGS with the former being something a little different.
Unless you saw some previous trailers that we didn't ... Bullshit. A big negative with this game is the marketing, specifically this long with no gameplay. If there was some trailer that had something we have an idea of what gameplay was like then that negative wouldn't exist.