Never heard of pastila before. I HOPE I remember having bookmarked the article once apple harvest season arrives. This link sounds wrong, but does take you to the correct Gastro Obscura page.
Pastilla, I know the Marocaine version, which is a savoury dish with layers of brick . Doesn’t look like the Russian dessert at all.
Different spelling, and the article says it’s from the Russian word for bed.