[P.S.] I realize I left off an important part: If the regular version did not already "reason"... Why would we ever expect this kind of tweak to change that, and bright forth real reasoning?

The core algorithm hasn't really changed, we're just changing the (hidden) document so that it's a different style with a greater density of clues, so that it can more-effectively bullshit [0] output humans won't notice and dislike.

[0] Creating something that "sounds good" without any particular awareness or care about truth or falsehood.

The steelman argument - not to say that I agree with it - is that this capability was present all along, but due to variability in the behavior of the model, adding certain context, such as chain-of-thought, exposes it.