ST_ConcaveHull returns polygon with holes despite allow_holes set to false

[nbvfgh]

Considering following query:

WITH data AS(
	SELECT ST_GeomFromText('POLYGON ((0 0, 1 0, 2 1, 1 1, 0 0),(0.2 0.1, 0.5 0.4, 0.5 0.3,0.2 0.1))'
	) geom
)
SELECT ST_AsText(ST_ConcaveHull(geom, 0.3, false))
	   from data;

-- expected:{ POLYGON((0 0,1 0,2 1,1 1,0 0))}
-- acutal:  { POLYGON((0 0,1 0,2 1,1 1,0 0),(0.2 0.1,0.5 0.4,0.5 0.3,0.2 0.1)) }

We calculate the concave hull of a Polygon With hole，and set param_allow_holes = false.
But the result still contains a hole when the optional param_allow_holes argument is specified as false, which seems to be unexpected.

The original input and result are shown in the following figure：

[dr-jts]

The concave hull is formed using the outer shells of the input polygons. The "allow holes" parameter controls whether holes are allowed to be formed in the additional area created for the concave hull. Holes already present in the input are preserved.