Yes, that is true. Think about it, an Elf owl can't eat as much as a snowy owl, or a Great Horned owl. Therefore, an Elf owl has to eat less, hence, smaller amount of undigestables in the stomach. Then this will result in a smaller Pellet.
I hoped that this helped!
depending on the food it eats where the pellet was found u can look in an owl pellet guide
to find out what the owl has eaten
The A hole
The owl pellet remans in the owls rectum until the owl decides it would be a good time to puke it out.
The outside of an owl pellet is covered in a thin slime, to assist the owl with ejecting the pellet, the undigested fur or feather tends to be the next layer, with the undigested bones on the inside.
An Eurasian Eagle owl is larger, though not noticibly. Only after studying them would one discover the size difference. The Eurasion Eagle Owl has a larger wingspan also.
The owl pellet shows what the owl has eaten.
pellet
The inside of an owl pellet contains the remains of bones and fur that was undigested.
Fur and bones of what the owl ate.
Any owl larger than the rabbit eats rabbits.
the size and shape