I found a sutta where the Buddha says it is hard to find any phenomena in this world that changes faster than the mind: “Aṅguttara Nikāya (1.48)“.
The short sutta says: “Nāhaṃ, bhikkhave, aññaṃ ekadhammampi samanupassāmi yaṃ evaṃ lahuparivattaṃ yathayidaṃ cittaṃ. Yāvañcidaṃ, bhikkhave, upamāpi na sukarā yāva lahuparivattaṃ cittan”ti.”
Translated: “I consider, bhikkhus, that there is no phenomenon that comes and goes so quickly as citta. It is not easy to find an analogy (a simile) to show how quickly citta can change.”
Modern science says there are many things that occur in the femto-second time scale. That is million billion times per second. So, citta could change faster than that, and therefore those quotations are correct regarding how fast citta can arise.