Thanks for your reply!
I was researching this website https://twitchtracker.com/
This website is using the Twitch helix API, and you can see a lot of info including sub count of almost all the streamers in Twitch.
I doubt the owner of the website requested permission to ALL streamers to get this data.
However can you explain why is this website able to get that info, because based on your statement
"The subcount of a streamer is data that is personal information.
As such you need permission from the streamer to read it."
And on this website you can basically see sub count of any streamer?
Thanks