Normal SAS considers a character variable with only spaces in it as a missing value. So I would expect that a variable that consists only of spaces would generate nothing in the CSV file as that is the normal way to represent a missing value. Perhaps CAS interprets those types of values differently? Perhaps it supports variable length character strings? Similarly missing numeric values should be represented by no characters in the file.
Here is a simple SAS data step to demonstrate how missing values normally appear in CSV files.
504 data test;
505 set sashelp.class (obs=3);
506 if _n_=1 then age=.;
507 if _n_=2 then sex=' ';
508 file log dsd ;
509 put (_all_) (+0);
510 run;
Alfred,M,,69,112.5
Alice,,13,56.5,84
Barbara,F,13,65.3,98
NOTE: There were 3 observations read from the data set SASHELP.CLASS.
NOTE: The data set WORK.TEST has 3 observations and 5 variables.
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