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.
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.