While I admire your teachers actions, I do question the final result of issuing an Instructor License (so to say) to a student that has yet to learn the entire art curriculum? (Unless by 4th Kyu you have all the knowledge of the art?) (No offense meant here by the by, you are probably a great instructor.)
None taken, happens a lot when I tell people that story and they assume exactly what you did.
To me an instructor (when it comes to martial arts) should be able to take any student at any level and train them in the next steps,
Agreed, in addition to what I stated in my first post.
and at 4th Kyu (provided full transmission has not happened till 1st, 2nd, 3rd/etc Dan) the student would stop getting valid content at 5th or 4th Kyu.
Not really true in our case.
In our system you do not just get an Instructors certification when you make your Dan ranks it is not automatic. It was always given by (until his death) the founder at his discretion based upon many things that he saw in a person to be able train to become an Instructor. All of our Blackbelts are not Instructors although very skilled, all people are not meant to be or have the ability to be what I descibed in my first post.
Yes, the 4th Kyu teaching will go up over time as well, but what I am saying is a 3rd Kyu, who has not received their instructors cert will not be able to learn and train under the 4th Kyu...
Our Instructors certification is very very different than what some would consider mainstream certification, we are able to instruct 1 level below all present and future ranks.
This would take care of the problem you pointed out.
While a non Dan student of the arts, be happy learning the arts, and strive to learn the art fully before beginning teaching others the art. There should be no hurry to get to teaching the art, but go at the pace of learning that allows you to fully grasp the art, learn its deeper meanings and reasonings of going it "that way".