You are correct, at least for mobile streaming using the YouTube app. Here is the link and offcial text, as of April of 2019:
We’ve recently raised the threshold for YouTube Live with a mobile device. To be able to live stream on mobile, your channel will need to have at least 1,000 subscribers.
Note that this eligibility threshold does not apply to other live streaming tools. Creators who have less than 1,000 subscribers will still be able to live stream through desktop and webcam.
Currently this does not appear to affect ScoreCam users but this could change at any moment and there is nothing we can do about any future changes.
Recommendations: Give Twitch a try as it seems to produce better quality videos and the lag time is a lot less. At least have it as a backup in case YouTube stops working for users with less than 1000 subscribers.Tags: live streaming, twitch, youtube