#42720 represents an update to Rollups wherein there will exist a dedicated Rollup Action along with a Rollup ILM action. Internally, this was nicknamed RollupV2. There are a few references to this in the codebase

• the rollup/v2 package
• the RollupV2Indexer
• the RollupV2 class
• the es.rollup_v2_feature_flag_enabled system property

these need to drop the V2 to be more descriptive of the final Rollup naming.