Many people are indicating otherwise. I don't see how the streaming service is connected to ShadowPlay.
thats because they dont know what it does
if you have shadowplay on, then disable the streaming service, shadowplay will work.
if you continue to also turn shadowplay off in geforce experience, you will no longer be able to turn shadowplay back on until the streaming service is restarted.
restarting streaming service has been a bugfix since the release of shadowplay, where the streaming service would sometimes disable itself.
try it yourself if you dont believe me. disable the service, disable shadowplay, then try to re-enable shadowplay afterwards.