Data can be cumulatively displayed in ArcGIS Pro. However, ArcGIS Pro does not enable the display data cumulatively option in the Layer Properties of time-enabled data as in ArcMap.
Unlike ArcMap, the option for visualizing temporal data in ArcGIS Pro is controlled by the time slider on the map level (instead of the layer level). This is because the intent of displaying temporal data with the time slider is to filter the data in the view and to have only one temporal extent at a time. The map's time is used to drive all layers with set time properties in the map. For more information on how temporal data is displayed in ArcGIS Pro, see ArcGIS Pro: Visualize temporal data using the time slider.
To display data cumulatively in ArcGIS Pro, enable and lock the start time of the time slider. This allows for cumulative display of temporal data of all time-enabled layers within the map and is applied to the temporal extent filter to all time-enabled layers in the map. For more information on enabling and locking the start time, see ArcGIS Help: Configure time slider settings.