I'm sure that lump sum purchase will outperform DCA on average if the asset is appreciating. Sometimes you might get a better return from DCA if the asset depreciates during the buying period, but more often than not the asset will appreciate (that's why you're buying it), so a lump sum is more likely to give a lower cost basis.

As you say, DCA makes sense if you're buying with cash flow because lump sum is not an option.