Its got nothing to do with Nintendo. Both Capcom and Ubisoft use an existing Chinese company for cloud streaming of their games. This isnt actually the first AC to use the cloud for streaming, that would be AC Brotherhood. Likewise there are other cloud games for Switch in Japan, not just these 2.
SE uses their own service I believe.
I saw that also Phantasy Star Online uses a Cloud version for Switch in Japan. So Capcom, Sega and Ubisoft seem to use the same service. You seem to have more information if you say that they use a chinese company. Any pointers for more infos?