Considering this is the same demo that was used at trade shows I'm going to assume that you start with an ample amount of potions and pick up more (+phoenix downs) along the way because they don't really want people getting a "Game Over" at the booth after queueing for hours to play it and then leaving the booth feeling miserable. IIRC the demo of FFVIII back in 1998 of the Dollet Mission gave players access to a bit more stuff item-wise (and even ability wise) than what they would normally have had at that point in the game.
Also, if they made the combat Souls level of difficulty from the first boss, the backlash they would've faced would be insane. FFVII is after all a beloved game, and the hype around this means that it's going to be bring in new and old alike. I think a Souls level of challenge type game from the first boss would immediately alienate a lot of that audience.
Do I think it's a tad on the easy side on Normal? Yes. Though am I also happy that magic and abilities are actually impactful after FFXV? Also yes.
From all the preview videos I've seen from press/influencers who got given a three hour demo to try recently which covered further parts of the game all commented on how the Air Buster fight at the Sector 5 reactor was challenging etc. (SPOILER)And also has an optional mechanic inside the reactor where you can find keycards to re-configure the boss before you fight it.
So I expect it to ramp up in that regard, but never really reach a Souls level unless they've snuck in some optional super bosses.
Who knows, maybe they'll even patch in a free harder difficulty like they did with KHIII.