Are values in STEP part 21 (ISO 10303-21) CAD files freely embeddable in entities?

Question

Are values in entities freely embeddable in an ISO 10303-21 formatted file?

In all the examples I've seen that were generated from CAD programs, length_measure is embedded in uncertainty_measure_with_unit, like this:

#83 = UNCERTAINTY_MEASURE_WITH_UNIT (LENGTH_MEASURE( 0.0001 ), #86, 'distance_accuracy_value', 'NONE');

Is this required? Could this be changed to, for example:

#83 = UNCERTAINTY_MEASURE_WITH_UNIT (#10000, #86, 'distance_accuracy_value', 'NONE');
#10000 = LENGTH_MEASURE( 0.0001 );

Conversely, we see something like this:

#91 = APPROVAL ( #92, 'UNSPECIFIED' ) ;
#92 = APPROVAL_STATUS ( 'not_yet_approved' ) ;

Assuming #92 is not used by any other entity, could this be changed to:

#91 = APPROVAL ( APPROVAL_STATUS ( 'not_yet_approved' ), 'UNSPECIFIED' ) ;

The reason I ask is, I don't have access to ISO 10303, since it is locked away behind many hundreds of dollars of paywall, and none of the sites dealing with STEP talk about embedding values.