My Gas dryer has three devices and my dishwasher has four. Each grouped into one device.
Thinking back, now that you mention it I initially had issues merging the fourth into the dishwasher. The fourth was active/on when I first tried to merge, Sense appeared to merge but the fourth was still listed separately even after the device went off. I repeated tried to merge them after the device went off but it didn’t merge into one.
Once they were all off, I un-merged all the dishwasher parts and re-merged them then they appeared as one device.