In what sense is Blender a customer if they aren't monetizing their videos, though?
> a person of a specified kind with whom one has to deal
[edit] Youtube has 3 kinds of customers (or users, if you wish): publishers, viewers and advertisers. It makes sense to separate them like that, but not based on a "pays/ does not pay" criterion. If PewDiePie is a customer, then most definitely Blender Foundation is a customer too.
Anyone having a YT channel will tell that ‘suggested video’ is a dominant traffic source so it’s not an edge case.
In sum, YT was already making money thanks to Blender videos.