You sound pretty hard on yourself. Im sure your Sensei isnt getting you mixed up, although it is hard to remember exactly who has learned what... He may just recognize the skills you have, and think you are ready for promotion. Im not sure if its this way in your class, but you can pass a belt test, even if you dont know every single technique. The test requirements are usually just a basic format for testing, and they give the student and instructor a basis for promoting. If you use one technique the entire Randori session and it works, then that "Same ole, same ole" technique is a great one. Aikido does focus on less techniques than other arts, but it has a focus on perfecting those techniques. So dont feel like using one technique is bad. Just remember that inside the dojo is where we practice. So use this place to try different techniques and remember no one is a master the first time they try something different. Good luck, and dont be so hard on yourself.