Then do you mean that, if I put after tax money into a savings account, let it build up, and withdraw it to buy stock, that money ceases to be "savings?" Even the government calculations don't go that far. The only differences between 401(k) equity investments and after tax equity investments are that taxes are deferred on 401(k) investments and are not on after tas equity investments, taxation is somewhat different, and there are a number of restrictions on withdrawls from 401(k) accounts. You're arguing a distinction without a difference.
Yes you've taken it out of savings to invest.
A 401k is an investment account not a savings account.