What does "is empty" mean?

[Bud]

ArcGIS Pro 2.6.8; Oracle 18c; 10.7.1 EGDB; SDE.ST_GEOMETRY

Regarding the isEmpty ST_GEOMETRY SQL function: 

ST_IsEmpty returns 1 (Oracle and SQLite) or t (PostgreSQL) if the ST_Geometry object is empty; otherwise, it returns 0 (Oracle and SQLite) or f (PostgreSQL).

It seems like an empty geometry can either be:

1. Shape is not null, and geometry is not null (geometry is Nil/zero-vertex), or
2. Shape is not null, but geometry is null

In other words, the shape is not null, and the geometry is either zero-vertex or null. 

Is that correct?

SQL testing:

select
    objectid,
    shape,
    (shape).points as geometry,
    sde.st_area(shape) as area,
    sde.st_isempty(shape) as is_empty,
    comment3,
    (shape).entity,
    sde.st_entity(shape),
    (shape).numpts
from
    infrastr.inf_record_sp

Related: Idea - Define "is empty" in the ST_GEOMETRY documentation