If the streamer is able to withdraw the fund, of course, he will say that he gets the money through successful withdrawal.
Now (however, as before) you can not trust anyone. The essence of the work of streamers is that they are purchasable, (I'm talking about the most popular ones) - if someone offers them a contract under which they will receive x10 compared to the income that the audience itself gives them (donations, subscriptions, etc.), then 99 out of 100 will agree without hesitation.
But we should not forget about the naivety of people - if they see how every evening a streamer loses 5-10 thousand dollars in a casino, then it is worth considering whether this is real money
I agree streamers are being sponsored, so basically they will promote the one sponsoring them since they are getting paid. I bet many of us know that. We just watch for entertainment or how their featured game works.
Some streamer admits that they are playing with sponsored money while others tend to hide it. The money involved is real, but often than not, they are not owned by the streamer.