How do Sappho's poems illustrate "economy of expression"?

Sappho's poetry demonstrates "economy of expression" via the sparse, reserved nature of the emotion contained within it. As a writer, Sappho is not overtly direct or emotional. Her poems are not full of wild, vibrant descriptions that pull the reader into an exciting poetic tour-de-force. Rather, the poems emit a pensive, almost quiet serenity. For example, "One Girl" demonstrates this in both stanzas:

I
Like the sweet apple which reddens upon the topmost bough,
Atop on the topmost twig,—which the pluckers forgot, somehow,—
Forget it not, nay; but got it not, for none could get it till now.
II
Like the wild hyacinth flower which on the hills is found,
Which the passing feet of the shepherds for ever tear and wound,
Until the purple blossom is trodden in the ground.

In the poem, Sappho uses simile to begin each stanza, but we are not told exactly what is being compared to the apple or the hyacinth. This forces the reader to explore for themselves, thus making the initial focus more distant. If a reader doesn't know what is like the apple or the hyacinth, they are left to try to solve a partial equation, which forces a more intimate focus and will probably make the reader identify even more strongly with the simile once they have imprinted their own experiences onto it. Sappho's "economy of expression" forces the reader to become more personally invested, thus making the poem richer.