We are not redefining what it means; that the source is available does not make it Open Source. It's pretty clear, but Google is the SSPL open source and you'll find pages and pages of EFF/FOSS etc articles and explanations why it cannot be open source because section 13. It's AGPL (which is Open Source) with that section added.
https://en.wikipedia.org/wiki/Server_Side_Public_License
From another comment: https://opensource.org/blog/the-sspl-is-not-an-open-source-l...