My Sensei actually solidified my belief in a recent class. He commented to the effect that in Japan, new students spend the first year as an uke. Only after that time are they allowed to actually learn the techniques. He further commented that this style wouldn't work in America, where we all want instant gratification.
You're Sensei is wrong, incidently. There are no mainstream schools of aikido in Japan that follow that procedure. They are conducted very much like classes in America.
As for testing, well, why wear a white belt? Why wear a keikogi at all? Why not just wear sweats or other durable, comfortable wear?
A sixth kyu has the same essential meaning as a shodan: it means you have achieved a certain understanding of techniques, that you can execute them if asked, and that you are ready for more responsibility than a dojo. It means no more, and no less. Why are there kyu ranks below shodan? Because there are varying levels of skill below shodan. The ranks give the instructors a rough understanding of those levels of skill. They wouldn't be necessary in a small, private dojo with only a few students, but they are useful in large organized dojo.
I think Michael O'Brien said it best: don't think anything of it. Take the test, accept the rank, and move on.