Thanks for the correction. But again it rarely matters in practice.

In practice it means that if you file for a green card while on O-1 status there will be 4-8 months during which you absolutely can't travel.

Ah, maybe I'm missing some subtleties. I was referring to "you're not supposed to have intent to immigrate on a X visa", which never seemed to matter as I personally applied for H1-B and a greencard while on a J1