One is the coming home at the evening hour and the other is the passing away to death. While Eliot's note about Sappho seems to indicate he meant the first, the allusion to Stevenson's Requiem in the words "sailor home from sea," where the theme and title is about death, strongly support the latter, especially when we consider the sailor's death in Part IV and the deaths of the other sailors in the draft for that section.
220) At the violet hour, the evening hour that strives
221) Homeward, and brings the sailor home from sea,
I think that the Sappho allusion is a sly hint for us to consider another allusion Eliot has used before and will again, an allusion to Walt Whitman's When Lilacs Last in the Dooryard Bloom'd where the first lines are (the great star represented the assassinated President Lincoln)
When lilacs last in the dooryard bloom'd,
And the great star early droop'd in the western sky in the night,
I mourn'd, and yet shall mourn with ever-returning spring.
Ever-returning spring, trinity sure to me you bring,
Lilac blooming perennial and drooping star in the west,
And thought of him I love.
Here is what Sappho had to say about Hesperus, the evening star in a poem fragment entitled You Are the Herdsman of the Evening:
Whitman's poem also describes the westward travel of the train carrying Lincoln's coffin from Washington to Springfield. This could figuratively be the star's herding of Lincoln's soul homeward and could be compared to Sappho's Hesperus as herdsman.
Hesperus, thou bringest home all things bright morning scattered;
thou bringest the sheep, the goat, the child to the mother.
Hesperus was the name of Venus as the evening star and Venus as the evening star always appears in the western sky.
See other Whitman allusions.