I have never understood this logic.
You just lost 10% of your entire portfolio, yet you take this "opportunity" to buy .01% of your portfolio at a good price.
Its a small silver lining...
The portfolio will come back eventually, so it is just a paper loss. In all of history, the stock market has always come back eventually. The buying opportunity may not ever come back (this could be your last true chance for the biggest gains). We may got more buying opportunities, or this may be the lowest point the stock market will ever be for the rest of time, we don't know. Every local minimum has a chance of being the last time the stock market was ever that low again.
Plus, it reinforces the buy-and-hold strategy which in practice almost always beats out the "perfect crystal ball that tells me both (A) when to get out and (B) when to get back in" strategy.
Your numbers also are off. The median (which will vary depending on age and other factors) retirement account balance is about $100k. Right now, you have a new year where you can put in $5500 or $6500 depending on age). That means we've had a ~10% correction, but the chance to add ~6% more to our retirement account at a good price (not 0.01%).