Specifying the RS=NONE option on MVS does allow this file to become more portable. The CC character '15'x is added mostly because of performance reasons. Specifying the RS=NONE option requires that we build one record at a time which I assumed would add some additional overhead. However benchmarking this has not proven a significant difference so far with my test.
I will enter a suggestion defect on this so that it can be considered for a future release.