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In the curved-tube image, clearly the ball will exit with a clockwise spinning, because it'll be rolling on the external wall of the tube (based on the "Newtonian principle" of inertia). I'll bet if you try it as a experiment (inside the atmosphere) the ball will follow "C"... Am I a confident idiot?

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That's a standard fallacy I often run into: over estimating second order effects. Yes, unless the ball is perfectly smooth or in a vacuum you will get slight curvature. But it would be so slight that it would look like B.

Try it with a ping-pong ball (a natural choice). The curvature coming out of the tube will not be slight.

None of the three choices in the diagram are curved, though.

I was actually thinking the same, shame there wasn't an answer in the article.

The "right" (too simplistic) answer in the article is "B".

"One group knew the right Newtonian principle: that the ball would continue in the direction it was going the instant it left the tube—Path B. Freed of the tube’s constraint, it would just go straight."

This is why science works well - it can tell us what the actual answer is, not just the one that is 'obviously right'.

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