No; short selling is NOT selling shares that you actually own - that's just selling shares; the brokerage does not "redefine" the sell as short - it's just a sell. You go from positive long shares to 0 shares. Once it settles, your brokerage account doesn't even show the stock in your portfolio, but will show it in your statement or in the gain/loss section.
Short selling is when you sell shares that you don't own. Period. After the short sell, your brokerage account shows a short position in the number of shares that you have sold - shares that you never owned.
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