it unnecesserily restricts possible type domain (we cannot assume the same type set for unknown exporter implementors)
it adds complexity of resolving type even if there is no need for it. Type of value does not add any value in case of basic types like boolean, date, string.
CellType could be renamed to TypeHint and modeled as attribute
CellType as enum has many design flaws:
CellType could be renamed to TypeHint and modeled as attribute