what is your WFS server?put its parameters on;

In my example the response was from the MapServer. But I can produce the same behaviour with the GeoServer. It doesn't seem to have a relation with the WFS server or the WFS version. After parsing a response with the ol format WFS I always get geometries with a faked Z dimension with value 0.

I don't know the reasoning, but the GML2 parser always produces a z value for a coordinate see:

See #6620 for an explanation. I don't know if what's written there is true though, so if anyone has an idea for a fix, a pull request would be welcome.

I don't know the reasoning, but the GML2 parser always produces a z value for a coordinate see:

openlayers/src/ol/format/GML2.js

Lines 90 to 99 in 16e6f37

	for (let i = 0, ii = coordsGroups.length; i < ii; i++) {
	const coords = coordsGroups[i].split(/,+/);
	const x = parseFloat(coords[0]);
	const y = parseFloat(coords[1]);
	const z = coords.length === 3 ? parseFloat(coords[2]) : 0;
	if (axisOrientation.substr(0, 2) === 'en') {
	flatCoordinates.push(x, y, z);
	} else {
	flatCoordinates.push(y, x, z);
	}

I think the format of (x,y) is diffrent of (x,y,0);the first is 2d,another is 3d;z=0 does not mean 2d;so fix it just add push(x,y) case;

@jacklinna I think that makes sense. Would you be able to create a pull request?