SIMD and data locality. You probably want to check across three vectors simultaneously and load the coordinates next to each other.

I'm guessing here. I haven't written video games in 20 years but struct packing/alignment was super important on the Sony PSP back then.

(author here) Both would work - doesn't fundamentally change the underlying idea. This particular representation is lifted from raytracing in one weekend and emphasizes the fact that we're really thinking of aabb as an intersection of three "slabs" of space. for me, it makes the ray intersection bit somewhat easier to explain.

Typically intersection checks outnumber updates, so it's better to optimize the former. Also, that only works if the object's pivot is at the center of the bounding box or you're accumulating movements without an explicit position.

That being said, a lot of tricks work better with center/extent instead of min/max, such as computing the AABB around an OBB or doing separating axis tests with abs() tricks. A bounding box and bounding sphere can also be stored together as center/extent/radius with only one additional value needed. Min/max works better for accumulation, though.