A complexType's shorthand content (no simpleContent/complexContent) has the
model (annotation?, (group|all|choice|sequence)?, (attribute|attributeGroup)*,
anyAttribute?). The existing content-shape check caught the wrong number of
model groups and content-spec exclusivity, but not the order, so a model group
after an attribute, an attribute after anyAttribute, or a second anyAttribute
(the ctB family) was accepted.
The complexType's direct children, excluding annotation and the content specs,
are matched against the same ordered slot model used for a complexContent
derivation.
XSTS: invalid schemas accepted 687 to 664, valid schemas rejected held at 72,
instance buckets unchanged.