On 29th August, this news post was posted to the Elastic blog.
Aside of the frankly weird writing style, the important TL;DR is in the second paragraph:
[LOVE.] The tl;dr is that we will be adding AGPL as another license option next to ELv2 and SSPL in the coming weeks. We never stopped believing and behaving like an open source community after we changed the license. But being able to use the term Open Source, by using AGPL, an OSI approved license, removes any questions, or fud, people might have.