Bryan: You are perfectly correct.
This is what I have been saying as well.
It's funny how Micheal simply assumes that certain things that apply to effectiveness against Judoka can only be learnt doing judo/jujutsu like randori or some other sort of resistance randori. I have another story with this point in mind (hope this one does not generate another explosion).
I attended a Judo technical training workshop with 7th Dan Judoka Steven Jimerfield recently. He instructed some of the finer points of competition Judo etc., including things like leg picks and more efficient variations of doing techs like ippon seoi nage etc.
What was interesting was that a lot of things he showed to make Judo techniques more energy and movement efficient came directly out of Aikido. One of my students joined me on that trip and he was catching hell to get things to work with his Judo partner at first, until I started to explain the Judo stuff in Aikido terms to him, and then he started to really get the stuff being taught. This was practice however, not randori.
Jimerfield had taught some interesting applications of tegatana while on the ground to block any sort of arm control techs like kesa gatame, and used a movement like that used in koshi nage to perform what he called "small man" ippon seoi nage.
At the end of it we had a little scrap session and the Judo folks found out a few things as well-
By always keeping weight low and posture straight, it was nearly impossible to get a leg pick on the Aikido folks there.
By using tegatana and tai sabaki effectively we could shut down most of the tachi waza and one or two of the ne waza. To the shock of some of the attendees.
On the other side the Aikido folk learnt that if you want to survive on the floor, harmonise with the concept of being a greased snake, else it's good night.
Also that the closer the hips are to the floor in ne waza pins the better.
This is not so much about randori sparring in Judo, but it may show to a point where the principles and methodologies taught in the different arts may not be as different as some might think and can be applicable in both directions with slight modifications sometimes. In my early Judo days, what had hampered me the most was my mindset from Aikido training that one was supposed to be cooperative - as soon as that left, things changed.
Like Bryan said - when you enter Judo range and ma ai and start grasping lapel and arm, your Aikido initiative has already left the building. At this point you're in Judo's domain, but it does not mean that there are not things that one can't apply from Aikido in a modified form that will be almost as effective as if the aikidoka had trained in judo to a certain degree. Of course this does not apply to everything in Judo, else we wouldn't have 2 different martial arts.
Just my 2 cents.