Sadly, this is due to a limitation in part of the YouTube Reporting API. Some reports have to be requested as a report job, and it may take 24-28 hours for that to be processed. For example, if the report is scheduled on May 1st, 2019 for that day's specific data, it will be ready on May 3rd, 2019.
Note that this does not impact all parts of the API and some data may be available day of. But if you see that there's a gap of missing current data, this is why.
For more information on this behavior, see: