In practice I have to agree with enrico-sorichetti.
JCL has gone through several iteration over the years, but it was never called a "version" change. I can recall when JCL did not provide keyword abbreviations like DSN in place of DSNAME, or VOL in place of VOLUME, but that was added at some point in OS/360. I can also recall when JCL did not provide STEPLIB, though that has more to do with program management than JCL. I can remember visiting a friend running a back level of OS/360 on a very stripped down 360/65 who sort of simulated STEPLIB like this -
//A EXEC PGM=IEFBR14
//PGM DD DISP=(SHR,PASS),DSNAME=library(program)
//B EXEC PGM=*.A.PGM
I remember thinking at the time that was very clever.
I think instream PROCs were added late in OS/360, but I could be wrong about that.
There have been many changes since MVS. The diagnostics have improved considerably, for example, and // OUTPUT was added. Another useful improvement is // JCLLIB.