That's because the withdrawals are 4%. If you have $3M, maybe lower the withdrawals to 1.25%. That would be the same as 4% of $1M.

I don't think that's accurate.

If I withdraw 4% of a $1M portfolio, I only have $960K left to compound.

If I withdraw 4% of a $3M portfolio, I should have $2.88M left to compound.

If the question is "Will your money last?" I would not expect the simulation results to be identical.

Edit: I failed here. Downvotes are right. I simulated it myself and saw the results. Leaving this comment here so others can learn from my mistake.

Same here

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.