Currently if you want all polygons in a raster zone to be output as a single multi-part polygon, you need to run Dissolve on the output. The use case I'm working with is watersheds, but I could see this use case required for other allocation outputs such as you get from EucAllocation or Cost Allocation.
This dissolve is extremely compute intensive and often fails of the total number of polygons is more than 50,000 or so. Seems to me the multi-parts could be more easily created during the Raster To Polygon process without requiring the intensive topology processing Dissolve requires.
It would be great if Raster To Polygon support an option for multi-part polygon output. This would save the geoprocessing required to get one feature per zone.