It's probably a combination of different things. My guess is that driving style + car/setup differences are the most impactful.
Notice that Leclerc trail brakes for longer as well. By keeping the brakes on, he tries to loosen the rear and force some rotation at the rear when the weight is shifted to the front. Then mid-apex he applies (some) throttle to shift the weight balance to the rear and manage any oversteer that might occur by giving the rear tires a little bit more grip.
When the car feels stable and ready to point out of there, he goes full throttle.
Very interesting, thank you for sharing. It shows what great technique Leclerc has. It's very hard to do what he does consistently. Even if it's faster, you risk losing laptime if you don't get it right.