For example, the base Observation profile says:

_<element> <path value="Observation.value[x]"/> _

But the StructureDefinition for http://hl7-fhir.github.io/lipid-report-cholesterol.profile.xml says:

_<element> <path value="Observation.valueQuantity"/> <short value="Cholesterol value"/> <definition value="Cholesterol value. If a result is not available, use the comments field."/> <comments value="[[snip]]"/> <requirements value="An observation exists to have a value, though it may not if it is in error, or it represents a group of observations."/> <min value="0"/> <max value="1"/> _

I can't understand how this squares with the "Interpretation notes" in http://hl7-fhir.github.io/structuredefinition.html#6.17.5, which say

element.type is used to specify which types may be used for this element. If there is more than one type, the element offers a choice of types and must have a name that terminates in "[x]". Names of elements that are choices retain the "[x]" in the name, even if a constraint on such an element limits the number of allowed types down to one.

Does the existing of the Observation.valueQuantity path in the snippet above preclude any other types of value (i.e. is this just a limitation in expressivity)?