Ah, i believe there is still considerable misunderstanding. . .I understand your point in why do I have to initialize the field when there is no field to initialize as the file hasn't been created
The point of not trying to initialize the input data area is that when a read is done, the data content from the record will be placed in that data area and any "initial values" will be overwritten and no longer available.
Opening a new sequential file as output (and writing some record(s) to it) will "create" that file - in coordination with what has been specified in the JCL.