You seem to be referring to a hypothetical choice between investing a large accumulation of cash at the start of a period and portioning it out over the period, but the actual recommendation for dollar cost averaging is about moving money into investments as it becomes available rather than accumulating cash and trying to time the market.

If you've already accumulated a large cash position, yes, it's almost always better to dump it in the market, but unless it was an unexpected windfall, that just means you were suboptimally failing to use DCA before.