Agreed… for scopes that measure levels in a file.

IRE does not visualize levels in a file.

IRE is an analog unit that measures voltage on an electrical wire. Since limited Y 235 and full Y 255 produce the same voltage on an electrical wire (700 mV reference white point), both those values should be 100 IRE. The values of the digital data are irrelevant. All that matters is the final voltage hitting a wire.

Agreed… for a scope that measures levels in a file.

IRE does not visualize levels in a file.

It measures voltage. Since the sRGB and BT.709 specs happen to put black at 0 mV and white at 700 mV, the 0-100 IRE range is implicitly tied to the black and white reference points. In order to know whether a Y value represents black/gray/white, it has to be interpreted in the context of the range flag. Therefore, the scope must adapt itself based on the range to calculate what final voltage will hit an electrical wire.

IRE is completely different from a digital waveform.

Only in limited range. Full range would be 0 and 255 because full Y 255 is the same white as limited Y 235, therefore it should get the same IRE value.

With IRE, the graticules are usually 0% and 100% because IRE is a percentage, not an absolute value. The only way it would make sense to move a percentage graticule is to represent the black and white points for a format that puts black somewhere other than 0% (like composite video where black is 7.5%). However, even if we were to do that, nothing changes because limited Y 235 and full Y 255 are the same white and land on the same voltage and the same IRE/percent. Since the IRE is the same for both ranges, there’s no other sensible place to move the graticules. They already represent the black and white points for both BT.709 and sRGB without any movement at all. Limited and full are two different ways of specifying the exact same color, therefore they will have exactly the same placement on an IRE scope.

IRE measures only the final result, not the path taken to get there. This makes it intrinsically different than a digital waveform.

For a digital waveform, yes, it can make sense to move the graticules to represent the black and white points depending on the range.