After all he does use debuggers. He said "I use gdb all the time, but I tend to use it not as a debugger, but as a disassembler on steroids that you can program

After all he does use debuggers. He said "I use gdb all the time, but I tend to use it not as a debugger, but as a disassembler on steroids that you can program." This indicates that he is using the debugger as a means to improve his mental models of the CPU / hardware.