It makes sense but some people refer to yonkyo as Sumi otoshi i dont know why. I think yonkyo can be resisted easily if you do yoga to strech your arms.
My understanding is that yonkyo and sumiotoshi are two different techniques. I've practiced an upward projecting yonkyo (at least, that's what I think it was called) while sumi otoshi is "corner drop
," isn't it?