Torque converter question

I know how a t brake works I was just curious why a person needs a big stall on a t brake car. I had a 5k verter in my car and left on the break at 4500 to 4800 never tried to launch higher that my stall...may have been doing it wrong.... but in my case why couldn't I have used a 3500 and left at 4500? Does the verter affect the engines ability to reach that rpm if the verter is locked?