SimplifyAsFeature removes degenerate segments. A segment is degenerate if its length is less than 2 * sqrt(2) * tolerance of the spatial reference. The spatial reference for your data has tolerance = 2.0E-5, so any segment with length less than 5.657E-5 is degenerate. The length of the two shortest segments in the polygon are 3.3E-5 and 4.3E-5, so they are removed.
Hope this helps.
Thank you for explanation! Can you say, this formula is just heuristic or it is something that absolutely right in any case? I'm going to not perform SimplifyAsFeature for this data to preserve those segments since I don't think they are degenerated. Or I should definitely simplify the polygon with this method?
But I've attached the test data that is FGDB with unsimplified polygon, so it is definitely can be stored in database without applying the specified formula. Also I'm able to output this polygon to a new feature class without any error. Anyway thanks for information!