If preserve_attributes = TRUE, the returned character vector retains
metadata attributes (unit, concept, namespace, label). The
"defined" class is always removed.
If preserve_attributes = FALSE (default), a plain character vector is
returned with all metadata stripped.
Use strip_attributes = TRUE when flattening or preparing data for
external pipelines, but keep the default when working with defined
vectors directly.
Base R's as.character() always drops all attributes and returns plain
character values. It is equivalent to:
as_character(x, strip_attributes = TRUE).