Why is John Ruskin’s autobiography Praeterita considered incomplete and unreliable as a chronology?

John Ruskin’s autobiography, Praeterita (1885–89), is considered incomplete and chronologically unreliable because it was written as a "shamelessly partial" account of his life.

The work is unfinished and intentionally omits significant aspects of his personal history, most notably his marriage. Rather than serving as a precise record of events, Praeterita functions primarily as a subtle and memorable exploration of the development of his own distinctive sensibility.1