That result is right. The Quick Check takes a withdrawal rate, not a dollar amount, and runs with taxes off, so it's scale invariant: $1M at 4% and $3M at 4% are the same simulation times three.

That's what lets it be instant and anonymous, since the whole answer space fits in a small grid I ship to your browser. It stops being true once taxes are on, which is what the full builder does. The page should say so. I'll add a line.