Hazlitt writes: “there is no single speech which can convey a satisfactory idea of his [Burke's] powers of mind: to do him justice, it would be necessary to quote all his works; the only specimen of Burke is, all that he wrote. With respect to most others speakers, a
specimen is generally enough, or more than enough.”

In order words, we need “all that he wrote” to have an adequate representation of Burke’s character. The idiom, here, has no
connotation of finality — has nothing in common with the meaning of “That’s all she wrote.” The expression “antedates World War II by a
century and a half” is not likely.