Yes same stage. If you breed 2 pokemon from the same evolutionary line for example Snivy and Servine the balls don't swap the both need to be the same sage also.I bred a regular female Exeggutor (I know this because it had a Dream Ball) with a Ditto. I tried breeding the offspring male with a female Alolan Exeggutor (this one was caught with an Ultra Ball)but it only produced Ultra Ball Exeggcutes.
It made sense because they were technically different. But I evolved the offspring Exeggcute from before and it evolved into Alolan Exeggcutor.
I think it's just I needed to evolve the Exeggcute to Exeggcutor. It only passed down Ultra Balls which tells me that both of them needs to be the same evolution.
The evolution still doesn't make sense though.