We will be pushing a Zuora for Salesforce maintenance release (Quotes 9.11) to all 9.9+ Sandbox orgs (including 9.9, 9.9.1 and 9.10) after 5 pm Pacific on Wednesday, Jan 30.
The push upgrade to all 9.9+ Production orgs will be scheduled for after 5 pm Pacific on Feb 6.
Quotes 9.11 provides fixes and enhancements. Please refer to the release notes for details.
Your post says 9.9+ will get update however the release notes say 9.10 only. I am assuming you are correct and suggest the release notes be updated.