draw:id on <draw:glue-point> inconsistent

19.189 draw:id
19.189.2 <draw:glue-point>

<quote>
The draw:id attribute assigns an identifier to a glue point. See 10.3.16. The ids 0 to 3 are reserved for the 4 standard glue points of drawing objects.
</quote>

so it seems that in this case the draw:id represents numbers, and accordingly its type is nonNegativeInteger.
but then the text states the relationship to the xml:id attribute:

<quote>
A <draw:glue-point> element shall not have a draw:id attribute if it has no xml:id attribute value.
The value of a draw:id attribute shall equal the value of an xml:id attribute on the same <draw:glue-point> element.
<quote>

but xml:id has the type ID, which is a specialization of NCName.

the lexical spaces of nonNegativeInteger and ID are disjoint,
so in effect no draw:id attribute can be used on <draw:glue-point> by a conforming ODF 1.2 implementation.

i do not know why the xml:id was added at this element; i think it was not added by the metadata work.

i am not sure how this problem should be resolved.
simply changing the type of draw:id to NCName would break compatibility with ODF 1.1.
maybe it would be best to remove xml:id from this element again.