You’re creating a straw man from what I said. My point is that if you start with lower contrast text by default, when you reduce it further for priority balance, you end up with text that violates accessibility guidelines (like the ancillary text on this page, and on Twitter). This text is even less legible in adverse conditions. What you are saying is that you don’t want people to be able to read this text. You keep saying “perfectly legible” when this is measurably untrue, using the guidelines we have for this.
By proposing starting from black text, I am saying to reset this default. Too-bright backgrounds can be adjusted with screen brightness. Too-small type by zooming. Too grey type has no user fix.