Proving the Break Flag is Fictitious (opens in new tab)

Technical discussions on the 6502’s Break Flag continue to show misunderstandings and confusion. There’s limits to what a test ROM could prove because someone could still say the break flag is just “hidden” and not directly accessible. So, I am trying to find where on the die to point people to to prove once and for all that the break flag only exists on the stack and not ever in the status register. This link seems to indicate that at some point visual6502 had information on the break flag: ...