Surface Grids Temperature Spread Unrealistic

[False Anomaly]

Surface grids have been feeling off, especially when it comes to collisions between planets. So I conducted a test.
Test 1: In US2 a23.2, I load the Earth & Moon collision simulation. The Moon collides with Earth, and in 2.5 hours, Earth is a molten ball as you'd expect.
Test 2: I do the same thing for US2 a24.1. This time, after 2.5 hours, Earth is still intact with its oceans, and the only parts affected by the collision are a bunch of grid pixels on the exposed side of Earth.

This is what I've been basing the test on: https://youtu.be/PnhflL7-I3I
It's not the same conditions, but the larger planet turns to a molten ball unlike Earth in the 2nd test, and the temperature appears to spread across the entire thing as it should do in US2, but doesn't.

What's going on here?

[False Anomaly]

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