AutoCAD supports more than one “group” type entity, namely Shape, Polyline and Block.
These can be recursive; for example, a block can contain another block, which contains a polyline.
Because group/continuous entities in EdgeCAM are not recursive, only the top level group entity is supported.
AutoCAD supports blocks that contain all types of entities, but EdgeCAM only supports groups that contain Lines, Arcs or Points. In this case the group only contains the compatible entity types.
Also, AutoCAD block entities can have elements of different colour/layer/style. This is not supported in EdgeCAM, so groups are created in the default block colour/layer/style. However, if the group is exploded, the different colours can be seen in the underlying entities.