Sure, if you have a lump sum to start with.

But dollar-cost-averaging beats saving up a lump sum and then investing.

I think the phrase you're looking for is "automatic investing" or something, not DCA. DCA is usually framed explicitly as a counterpart to lump sum of an existing pile of money

DCA in my understanding is automatically investing a fixed amount at fixed intervals. E.g. $100/month, or whatever. The amount and interval aren't all that critical. The point is to do it automatically and not try to time the market.

Yes I also have heard the advice to dollar cost average a lump sum, not so much in the scenario of a rollover of an existing investment, but when a large amount of cash has become available for some reason. I guess the theory there is you won't accidentally put it all in at a market high point. If you average it in over a year in a declining market, you're better off. If you average it in to a rising market you're worse off than if you had invested it all up front. Trying to guess which of these scenarios is going to happen is trying to time the market. I'm sure people have done the research -- intuitively, if you're investing for the long term, better to put it all in at once. But there are probably risk tolerance considerations.

A year is pretty extreme. If you cut a lump sum into a series of transactions over a couple weeks or even days it is just about the least expensive way to exchange earning potential for reduced volatility. You miss out on like 2 weeks of earnings in exchange for a huge reduction in the chance that you buy in and are immediately down 2% or something.

You can do both. You can invest the entire amount, but make it short/medium bond heavy on Day 1. As you go thru the year, you rotate more and more of your fixed income allocation towards equity until you reach your target equity %. This is relevant if, for example, you downsized your home or received a retirement payout.

There's just as much probability that you miss out on a big swing up as there is that you miss a big a drop.

It's not the big swings you're trying to avoid, you're just trying to average together a bunch of interday minor ups and downs so your starting price is not as volatile.

Depending on the definition of “beating”. On average investing right away is better but the variance of outcomes is higher.

On average across all investors. Not so much if you invested at the peak of dot.com (would have taken decades to break even) or even the covid bubble.