[Cura 3.6] Slices with no result, unless turned 90 degrees

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Somewhat confused why the attached STL when sliced using 3.6 (using stock settings for an Anycubic I3 Mega, 0.2mm layers) creates a result with no layers, but if I rotate it 90 degrees works fine.

TallSquare.stl

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Found the "Print Thin Walls" setting that now has it printing without rotating.  But since the thickness didn't change, why would rotating it 90 matter?