Weaving Effect feels too inconsistent

Often times when a mob dies with the Weaving effect there is no cobweb placed around them. Even with plenty of space to do so.

I made a 7x7x7 space for cobwebs to spawn around killed mobs with the weaving effect and even when killing 10 mobs with sweeping edge, there are only like 3 cobwebs generated.

I expected at least 1 to generate per death with all the available space.