Salesforce added the option to configure multiple features in the DX Project Configuration file. One of the is breaking down the big CustomLabels file into individual files where we no longer need to deploy the whole file but just a file (label) that has changes in. Please see SFDX Documentation here - https://developer.salesforce.com/docs/atlas.en-us.sfdx_dev.meta/sfdx_dev/sfdx_dev_ws_config.htm