The Scheduler component introduced a new configuration property (rowHeaderColumnsMergeParents) and the Gantt chart inherited the default value:
https://api.daypilot.org/daypilot-scheduler-rowheadercolumnsmergeparents/
In the latest sandbox build (2022.4.5454), the Gantt chart now sets this value to false by default:
https://release.daypilot.org/changes/js/