Why listen once and not just listen to the channel

[Gbahaa]

trafficstars

in sagas.js, why do we need to listen to the data at a specific path once at the beginning while listening to the channel alone seem working and do the same job, code is here
https://github.com/rmrs/react-native-redux-saga-firebase-patterns/blob/f8ae2916086d30b2f5fa23abe21aa19a6baa8e42/sagas.js#L104

Am I missing something?