If you’re into finding out yourself: Can you spot the pattern in the deviation you see? Did you notice they both have mean 0? Look at y1/y2.
It does use the same formula but the formula does not say which variance estimate to use, so you picked the one that’s not the one *Norm uses: you have unbiased=True, *Norm uses unbiased=False. If you do fix this, you’ll get the same up to numerical precision.