I have run into so many people that believe if they tap out a higher belt they should receive that same belt. Although this is sometimes true, most of the time it is incorrect. We need to first understand that the art of brazilian jiu jitsu and submission grappling is more than just trying to tapout all of the higher belts and receive your black belt as quickly as possible. There is so much to learn in bjj and it takes years to even begin to understand the art. Looking back into my own training I realize now after 10 years of training I am only just beginning to scratch the surface of understanding this art form.
There are many reasons a lower belt may tapout a higher belt. The higher belt may be having an off day, your bjj game may just be well suited to beat the upper belts specific style, you may be a lot younger/stronger/more athletic/ heavier than the upper belt, or the upper belt may be working on parts of his game that are newer to him. I can remember multiple occasions as a blue belt where I managed to defeat purple and brown belts. I even managed to tap out my instructor 3 times in a row a week before he got his black belt, but I would never say I deserved to be a black belt at that time. I happened to find a weakness in my instructor’s game and was able to grab the same foot lock 3 times.
One of the biggest differences between lower and higher belts is the understanding of movement and how it relates to our art form. A lower belt takes longer to learn new moves because he will not completely understand the motor patterns required to do the movement and will not have a deep understanding of why the move is used. If you were to show a black belt a newer move they will be able to understand it and start using it almost immediately. An example of this is the day after I caught my instructor he asked me to start in the same position I caught him the previous day so he could see what I did. He worked on a few escapes and later when we sparred again I went for that same foot lock and never came close to getting it. My instructor’s understanding and level of jiu jitsu was so much higher than mine he was able to figure out how to stop me overnight.
Being competitive and trying hard to progress is never a bad thing. Just remember that bjj is a journey rather than a sprint. During your time you will learn so much and when you think you know everything you will suddenly realize you only just started learning. Good luck with your journey.