And if someone has strong enough technique to control me well enough to get to the point where he can use a pressure point without me be able to stop it, then he could easily throw me without even using the pressure point. So I don't see much need for such training, and I think they often are a distraction from studying how to control someone structurally and maybe even a crutch for those with little or no understanding of how to do this.
From a structural perspective, yonkyo is actually quite a simple technique, certainly easier to do correctly than nikyo or ever sankyo, and perhaps even easier than ikkyo.
By and large joint locks are marginally effective, and dicey with anyone traned. I just had an all day session with DR Aikido and CMA folks, with joint locks brought up and completely neutralized at every turn. People really need to get past these ridiculous assumptions of effectiveness, and help each other learn to stop these type of things. Leave it for work on non martial people. Maybe good for LEO on drunks or domestics. For us, learn em, know em, forget em.
It is the how and with what that you can neutralize them that has value. For that training also leads to neutralizing throws, and getting heavy hands and legs to strike.