Note 94 — Chapter XXVII · PARMENIDES.
Reading edition
Steinhart represents this idea of τὸ ἐξαίφνης — the extra-temporal break or zero of transition — as an important progress made by Plato, compared with the Theætêtus, because it breaks down the absoluten Gegensatz between Sein and Werden, Ruhe and Bewegung (Einleitung zum Parmen. p. 309).
Surely, if Plato had considered it a progress, we should have seen the same idea repeated in various other dialogues — which is not the case.