I agree, and I think it also has something to do with the fact that they associate masturbation with homosexuality, which comes across pretty strongly in the WTS literature.
They live in horror of homosexuality, so I think they're trying to find ways of preventing it, as they think of it as something to be cured or prevented, like a disease.
Haven't they figured out that most men are still heterosexual even though they masturbate?
Actually, that's a very Victorian era fear, it's been disproved by sexual research way back, but during the late 1800s, early 1900s, it was a popular theory explaining homosexuality.
But, yes, anything pleasurable must be controlled. It's like you have to do all their work first before you get access to pleasure or entertainment, which is just more WTS micromanaging so they can get their work done for free by lots of people trying to work their way into God's favor.