As part of Google deprecating the old Google Search Console APIs, Google won't be supporting showing the indexed count within the sitemaps commands. Google's John Mueller confirmed this on Twitter.
John Mueller from Google said "As we removed that functionality from the UI a while back, we're no longer returning sitemaps indexed counts in the API either." "We should have communicated this better - sorry for the hassles," he added.
Here are screen shots of the API returning 0 for indexed counts, but the interface showing 120 valid URLs submitted. The API just shows 129 submitted but according to the interface, 120 are valid and 9 have errors.
@johnmu is the search console sitemaps api v3 getting deprecated? newly submited sitemaps don't get a data update for weeks. see screenshots API vs. new googel search console - it's not an issolated issue but happens over lots of sites cc @googlewmc @dannysullivan @searchliaison pic.twitter.com/opqYpzHJKk
— franz enzenhofer 👾 (@enzenhofer) June 7, 2019
Forum discussion at Twitter.