draw:type and draw:engine interaction

We have:

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10.6.2 <draw:enhanced-geometry>
The <draw:enhanced-geometry> element contains the geometry for a <draw:custom-
shape> element if its draw:engine attribute has been omitted.

19.146 draw:engine
The draw:engine attribute specifies the name of a specific rendering engine that can be used to
render a custom shape.
The value of the draw:engine attribute shall not influence the geometry of a shape.
The draw:engine attribute is usable with the following element: <draw:custom-shape>
10.6.1.
The draw:engine attribute has the data type namespacedToken 18.3.19.

19.229.3 draw:type for <draw:enhanced-geometry>
The defined values for the draw:type attribute are:
● non-primitive: no shape type is available.
● a value of type string: a rendering engine specific name of a shape.
The value of this attribute shall not influence the geometry of the shape.
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If draw:type is not set to non-primitive, the shape type is supposed to be engine specific. Unfortunately we do not seem to require that a draw:engine is defined (and at least one implementation specifies non-primitive draw:type without specifying a draw:engine). Since draw:type has no namespace, it is impossible to interpret draw:type when no draw:engine is given.

Note that the description of draw:enhanced-geometry seems to imply that draw:enhanced-geometry (and so draw:type) is only used if draw:engine is omitted.