Why simplify() returns unbounded polygon? Google Earth Engine

Why does simplify() return an unbounded geometry when the maxError parameter is above a certain threshold? I have a feature from RESOLVE ecoregions, when I specify maxError of 4 km it returns a nice simplified geometry, but when I up the maxError to 5 km it returns an unbounded geometry.

simplify(4000) vs simplify(5000):

Code and link below:

var ecoregions = ee.FeatureCollection("RESOLVE/ECOREGIONS/2017");
var geometry = ee.Geometry.Point([-151.06, 61.67]);

var simpError1 = 4000;
var simpError2 = 5000;

var myRegion = ee.Feature(ecoregions.filterBounds(geometry).first());

Map.addLayer(myRegion,{},'an ecoregion', false);
Map.addLayer(myRegion.simplify(simpError1),{},'low error simplify');
Map.addLayer(myRegion.simplify(simpError2),{},'high error simplify');

https://code.earthengine.google.com/7636a43eef5b2054e483bcc1ed7f12bd