I am but a humble Shrimp.

[Moonface]

By opening, do they mean just the very first area? Because if they're just talking about running past the wolf at the start of Bloodborne and getting through the gate, that is probably the easiest in the Soulsbourne series. Unless they mean the entire opening area of the game plus the first boss.

I assume they meant the opening area up until the first compulsory boss (excluding any of the bosses that exist purely to kill you in the opening such as in Sekiro), since they mentioned more enemies than just the wolf and few people standing around outside that building at the start of Bloodborne.

It's kind of a tough call on that one though. Demon's Souls initial area is a tutorial, and only the boss at the end can really be considered tough about it. Though it's very easy to beat the boss unless you're completely new, because all you have to do is stay behind it the entire fight and it'll never hit you. The only thing tough about the opening of Demon's Souls is that if you die to the tutorial boss, you don't get another chance at it, and you lose out on some bonus goodies for beating it that can give you a bit of a start in the game. So if you die, you don't get punished by having to do the area over again, instead you get punished by losing out on a chunk of items.

Which boss is that? I'm aware of some troll looking thing that can sit on you in some small room and then there's the big flame dragon looking thing that if you die to it in the beginning then you just fight it again much later in the game, but because of how the latter works I assume it's the former? Or am I forgetting another boss? Demon's Souls being easy would make sense since wasn't that the first time FromSoft did any game of that nature, and so can't expect anyone to have experience from another one of their titles going into it and if it was their first venture then the beginning would probably be a little easier than most other games so that nobody would get entirely turned off and instead see that it is doable, but you need to learn how things work in far more depth than just what the tutorial shows.

tl;dr - None of the openings are particularly hard unless you're a super scrub or completely brand new to the game.

Yeah, the streamer discussing this was mostly debating which game just had the hardest curve or area when going into it blind for the first time where you don't know what you're going to be up against or which was the hardest for someone going into any of them with zero experience in a FromSoft game. I've only done Bloodborne and Sekiro but the latter is definitely harder, because whereas Bloodborne has forgiving parrying, Sekiro does not. You either get the prompt at the split second window given to you for a parry or you're in for a very bad time. A lot of people describe the first Genichiro fight at the top of the tower to be the wall that tells a player if they've actually grasped the parrying mechanics well enough yet. If you can't beat him, you ain't beating nothing after him, and there's no builds to abuse like all the other FromSoft games have.