In 2021, a comprehensive review of Must Support was requested. This work began in 2021 and continued into 2022. The branch regarding this work was eventually merged here: 

https://github.com/HL7/fhir-ips/pull/22

Here is a link to a presentation that summarizes the major changes: https://docs.google.com/presentation/d/1KlHdMd8Gr2SYxTfFqF5FdgvsMrwWtTUXqP0Wld6fwFo/ (presentation also attached as PDF)

• There are currently over 400 Must Support (MS) statements in IPS
• Derived profiles from IPS cannot subtract MS statements
• A proposal to reduce Must Support in IPS was to look back at the ISO 27269 IPS dataset and limit the assignment of Must Support to items where “Required if Known (RK)” was assigned for the element and remove Must Support statements from optional sections / resources. A branch has been created to reduce Must Support based on the above proposal. 
• Reduction in Must Support to 232 in current branch