Clearing the xyWrite command line to run an xpl pgm wipes out four pieces of information that if known would let the pgm work as subtly as a function. Assembling any three of the four isn't difficult for experienced xpl programmers, but seizing all four defeated the most ingenious.
Documentation suggests interesting ways to mix the auxiliaries.
Runtime libraries, however, do change. It's all gain, no pain. Documentation explains why, and how you can start doing it. The overlay's structure is fragmented for versatility and to minimize memory overhead. When xyWrite makes so many resources available, an excessive devotion to tidiness is the only explanation I can think of for the impulse to lean exclusively on one instead of using the one best suited to the task.