The API does not return ‘pending rewards’
Note that api.algoexplorer.io is different from the API described on https://developer.algorand.org/docs/algod-rest-paths
This later API provides pending rewards. To access it, you can run a node (https://developer.algorand.org/docs/introduction-installing-node) or use PureStake API (https://www.purestake.com/technology/algorand-api/)
We’ll add that information in the next release.