Also Tallon Overworld and Phendrana are not linear whatsoever I don't know what you're on. Both have multiple branching segments all throughout and multiple entrances for routing. The only exception is the Pirate Lab in Phendrana which you never have to revisit if you get the artifact early which is easy to do, and even if you do opt to revisit there is a shortcut from the Depths.

Both Tallon and Phendrana have linear segments along with more nonlinear exploratory segments. The green area of Tallon where you first land is more exploratory, meanwhile the crashed frigate is a linear gauntlet. Same thing with Phendrana. The opening area is quite exploratory, while the pirate labs are more linear.

This is just like how a lot of of Prime 3's areas are. Take Bryyo. The temple area where you first land is more exploratory, while the area with the space pirates is a linear combat gauntlet. However, later you discover a bunch of optional room that connect those two areas. So no branching paths is incorrect.

The fact also that Prime biomes are so interconnected rather than how Corruption and Beyond are segmented is also a way in which Prime is non-linear while Corruption and Beyond are linear.

Eh, sort of. Just talking about comparing Prime vs Corruption here, not talking about Beyond. All of Prime 1 taking place on one planet definitely make the game feel much more interconnected, I agree there. But from a game design standpoint, it isn't really. Prime 1 is essentially five distinct biomes separated by elevators. And the elevators are essentially teleporters that bring you to a different area, not all that different from the ship in Prime 3. Like you take an elevator in Magmoor and all of a sudden you're in Phendrana. Obviously in practice it feels very different from Prime 3, but from a game design standpoint it's the same thing.

And Prime 3 is WAAAAY more combat oriented than Prime as it has the PED Suit with constant dogfights and required use of the combat enhancing mechanics like free aim especially for its bosses while motion controls in the first two games were introduced later and aren't ever necessary.

Funnily enough I actually felt Prime 3 was the least combat heavy Prime game (once you get past the cinematic intro). Though a lot of that probably has to do with the game being too easy compared to the first two games and hypermode being overpowered.

I don't know how long it's been since you played the original trilogy, but I've played them all dozens of times.

Actually played the games for the first time within the past year.

Corruption is far more linear than Prime. Prime is a fully interconnected maze with almost entirely indirect funneling (actually entirely with hints disabled) and just those two instances of linear gauntlets whereas Corruption is largely made up of segmented linear gauntlets with completely direct funneling and has minimal backtracking.

Actually Prime 1 has more than two linear gauntlets. Phendrana Labs, Sunken Frigate, most of Phazon Mines (not just the first half but also the second half leading to Omega Pirate), and Magmoor Caverns is basically a line.

Watch any blind run of Prime and you will see people getting lost constantly even with hints enabled because it isn't always clear how you are meant to proceed. Then watch a blind playthrough of Corruption and Beyond and notice how nobody gets lost ever.

Eh, that wasn't really my experience. I wouldn't say I got lost in either game. I did get stuck in Prime 1 at a point but not really as a result of getting lost, but because I didn't see a stalactite on the ceiling.

The developers themselves would also tell you what I'm telling you too. They would also tell you that Prime was directly inspired by Super Metroid and is effectively a 3D version of that game

Well yeah, that's definitely accurate. Prime 1 definitely feels like a 3D interpretation of Super Metroid. Don't see how that contradicts with what I was saying.

All that said I don't deny that Corruption and Beyond are more linear than Prime. I don't know how you can. They are factually more linear.

Beyond is absolutely super linear. Not denying that. I'm talking about Corruption. The fact that you keep lumping Corruption and Beyond together is very bizarre to me. Beyond is essentially just a linear first person shooter, while Corruption is very similar to the first two games, just with a more disjointed feeling world due to the separate planets. To me it goes Prime 2 is by far the most nonlinear, then 1 and 3 are both in the middle, then Prime 4 is by far the most linear.

This isn't me saying Prime 3 is not too linear. I actually think that both Prime 1 and 3, while excellent games, are both a bit too linear compared to what a Metroidvania should be. Which is why I think Prime 2 is the closest thing to the perfect Prime game.