I question the idea that "real" swordsmanship improves aikido more than properly understood Aikiken.
I hope you did not get that impression from anything I wrote. I think I've been very clear. I see aikiken as a specialized system created to advance and support the understanding of aikido principles. Furthermore, not all kenjutsu traditions may be conducive to supporting aikido principles because their core principles may be in conflict with those of aikido. When I observe Jigen ryu, for instance, I do not see an art that would be particularly valuable to an aikidoka. Jigen ryu just doesn't operate in the same physical plane as aikido.
In most koryu-sogo bujutsu schools (comprehensive martial systems) you might find things a bit different. The foundation of a sogo bujutsu is almost always kenjutsu. Consequently, the associated taijutsu/jujutsu system stands on the same basic movements and physical principles utilized in the schools kenjutsu. In fact, all the different systems taught in a sogo bujutsu will embrace one set of cohesive principles, whether you are wielding a sword, spear, knife or executing a jujutsu technique. So, "real" swordsmanship would only be valuable to an aikidoka if that sword system embraced complimentary principles, and since aiki originated in Japan as a principle of swordsmanship, there are numerous systems of kenjutsu that aikidoka enjoy as complimentary study.
So, you may be misunderstanding. I don't think anyone is claiming kenjutsu is superior to proper aikiken as a comprehensive part of aikido training....unless as an aikidoka you also want to be a swordsman. The controversy occurs the other direction, when someone doing aikiken, mistakenly believes aikiken to be "kenjutsu" and believes themselves to be a qualified swordsman.
I have many aikidoka with top notch experience in aikiken now training with me in TSYR. One is the US Chief Instructor of JAA. Others are from Shirata's Aikido system and Iwama style. Without exception, they will all tell you exactly what I am saying. Aikiken is an excellent training device for aikido, unless an aikidoka desires to go farther in their understanding of swordsmanship. If that is the case, they should search out a system of koryu kenjutsu, but that system should embrace principles complimentary to those in aikido, otherwise you face the challenge of learning two arts with conflicting principles.