There's a lot of FarCry/Ubisoft in this game absolutely.
But it's the movement and the freedom the grappling hook gives that reminds me of BotW. When I see something high up, I don't look for a road. I shoot to the top. There's no wall in front of me I can't overcome or have to wait to get over, or have to find the correct way to navigate (Within the set area at least). Doesn't matter how high the cliff is I'm jumping it. Very much not like Skyrim or FarCry where you can't jump everything in front of you (Well, actually Skyrim you can but due to jank not design)
Also the weapons are all available from the get go. As soon as you touch the open world everything is there to use. As opposed to FarCry games where weapons/throwables tend to be unlockable stuff you need to progress to get. Halo is closer to BotW where it's all there, and all disposable. You use it and throw it away. So in these ways it feels like BotW to me.
I find myself exploring all the time too. Generally I find nothing, which is kind of eh, but I still can't stop myself jumping up and down these hexagonal pillars, searching crashed ships, checking the corners of the map. The other day I'm pretty sure I found a secret ramp on top of a cliff, but I couldn't get a car up there. But I'm sure it's a thing. So the exploration is there for me, but it's not as fulfilling as BotW, absolutely.
Finding the Black Skull the other day was really fun. Fair enough I wandered over an area then a marker showed me it was there, but it still took me 30-45mins to find. So there is some cool exploring here.
I'm not saying it's a BotW clone, neither am I saying I think it's in the same league as that game when it comes too traversal, exploring, open world design, being player driven, etc. But I see bits of it and when there are reports saying that oh, it was meant to be like this, but they scaled back. I think I can see that. There are ideas in place here that would be the ground work for that. But there's also tonnes of FarCry/Ubisoft here as well. The side missions, checklists and progression is much closer to those games.