For those who plan to use this app long term, they may desire to have a more robust selection of verses under one collection. If someone is wanting to create a collection of verses about love from their devotions, they would quickly run out of space. Allowing for more than 20 verses allows someone to include as many verses as they would like without fear of not having enough space.
This feature would also be useful if someone is wanting to simply place all of the verses they learn in one year into a collection. This allows for easy tracking of how many verses they have actually memorized that year.
Perhaps a church is wanting to use this app for memorizing with a specific group (youth, adult Sunday school, etc.). They too would likely run out of room with the limited number of verses allowed in a collection.