JCL double substitution and conditional substitution

Hello All.
Occasionally find this article [https://www.mainframemaster.com/tutorials/jcl/quick-reference/symbolic-substitution-delimiters]
I suppose, an example

``
//STEP1   EXEC PGM=MYPGM
//         SET  PREFIX=PROD
//         SET  SUFFIX=DATA
//INPUT   DD DSN=&PREFIX..&SUFFIX,
//           DISP=SHR
//*
// IF (STEP1.RC = 0) THEN
//         SET  STATUS=SUCCESS
// ELSE
//         SET  STATUS=FAILURE
// ENDIF
//*
//STEP2   EXEC PGM=REPORTER,PARM='&STATUS'

would never works as expected: &STATUS value would be always FAILURE. IBM z/OS 3.1 SA23-1385-60 MVS JCL Reference page 38 clearly state:

If you define duplicate JCL symbols on a SET statement, the system assigns the last substitution text
to the JCL symbol.
Note: The substitution text specified on the SET statement is assigned to the JCL symbol regardless of
the logic of the construct. This is because the SET statement is not executed conditionally (such as in
the THEN and ELSE clauses of an IF/THEN/ELSE/ENDIF statement construct)

Furthermore, the next example

//STEP1   EXEC PGM=MYPGM
//         SET  ENV=PROD
//         SET  PRODDSN=PRODUCTION.MASTER
//         SET  TESTDSN=TEST.MASTER
//INPUT   DD DSN=&&&ENV.DSN,
//           DISP=SHR

is completely wrong. Double substitution in JCL impossible, because JES2 perform job conversion in single scan. So, DSN would be &&PRODDSN rather than PRODUCTION.MASTER.DSN.
Did you ever try check these example? I did, on z/OS 2.5 (as you state) and z/OS 3.1. Of course, both example failed...

Regards,
Gregory