I'm trying to calculate the concave hull of a point cloud (brown points in attached graph) using PostGIS 3.1.3 but am getting quite inaccurate results (red lines using target percentage values of 0.01, 0.1, 0.5, 0.8) despite using a relatively low target_percent value. Doing the same in QGIS via the Vector geometry -> "Concave hull (alpha shapes)" function (and a threshold setting of 0.1) yields better results (orange opaque polygon).

I am wondering if I'm doing something wrong?

Query:

CREATE TABLE public.sam_sm_gridded_seismicity_source_09_m4_0_00001 AS
SELECT ST_ConcaveHull(ST_Collect(geom), 0.00001, True)
FROM ssm_geoms.sam_sm_gridded_seismicity_source_09_m4;

Setup: POSTGIS="3.1.3 008d2db" [EXTENSION] PGSQL="130" GEOS="3.8.1-CAPI-1.13.3" PROJ="8.0.0" LIBXML="2.9.1" LIBJSON="0.15" PostgreSQL 13.4 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit