As the gas rose, people clambered over one another instinctively towards the still unpoisoned air above. Claw marks would be people trying to get higher.

Okay, that's your speculation though.

I know Zyklon B is a gas, that's why they're called gas chambers. Hydrogen cyanide is lighter than air so will rise to the ceiling first. So it would be counter productive to climb higher and it would have been pretty obvious considering the gas had a strong smell.

none of that dye would remain after so many years exposed to the elements.

Yeah the walls are covered in severe discolouration presumably due to the elements, as well as that there's all sorts of graffiti on the walls. If the scratch marks were made in 40s, why are they not discoloured too, and why are they lightly coloured like all the other graffiti there?

The only reason I can possibly think of to support the existence of those scratches being real is because people were in darkness in the chamber and were trying to climb the walls because they couldn't see anything. But even that doesn't explain why the scratches are so fresh on walls that have 70 years of discolouration, and why the recent graffiti looks the same colour as the scratches.

Recreating historical events is ubiquitous, even when it's horrific, and if anything I'd argue that the more horrific the more important it is to show people as accurately as possible what it was like.

Those examples you mentioned were clearly recreations whereas these scratches are made out to be real, made by the victims. I disagree with historical revisionism. Something shouldn't be put forward as truth when it isn't truth.