Mori V'Rabi doesn't know

 

In Shulchan Aruch (Y.D. 283) it says One may not write a מגילה with only a  few פרשיות of the Torah. When writing a Chumash one must write a complete Torah with all the (פרשיות - (חמשה חומשי תורה.  The ט"ז writes, that being it is too expensive to write a complete  Torah for children learning Chumash, therefore, Poskim were lenient and allowed  to write a מגילה with just a few פרשיות. The היתר is based on the Pasuk עת לעשות לה' הפרו תורתך. There are times when we don't follow the Halacha for a greater benefit. The היתר is only for this purpose so children will be able to learn. Mori V’rabi Harav Hagaon R. Shlomo Miller Shlita said he doesn't know of a reason to be מתיר to write the פרשת קטרת on a קלף. He does not know why a Segulah should be  enough of a reason of "הפרו תורתך"