This field has no property getter for optimization reason.
It is not read-only because when accessing it through RecordCellValue, a sequence is getting transformed into an array and the array is assigned to this field.

Reference

Record<T0,T1,T2,T3,T4,T5,T6,T7,T8,T9> Class
Record<T0,T1,T2,T3,T4,T5,T6,T7,T8,T9> Members