Sorry, I was wrong in my message, I’ve messed up between your parameters and the one’s from the tutorial.
I just did the exact thing as you, and I can at least confirm your results (and got same warning), here mine:
Default precision:
Total execution time = 1.328 sec
Max memory used by tensors = 1367458816 bytes

Mixed precision:
Total execution time = 1.236 sec
Max memory used by tensors = 1434552832 bytes