This is an environmental regulatory requirement by the Federal Bureau of Land Management.

They aren't referring to the regulatory requirement, but the response, I think?

Like if people can put in this much time and effort in a remote desert environment to meet regulatory requirements, and document their efforts so thoroughly, why can't corpos?

for the curios or those that skipped over it:

"Black Rock City is only allowed to return to the playa each year if it passes a strict post-event inspection from the Bureau of Land Management (BLM): No more than one square foot of debris can remain per acre (0.23 m²/ha)."

Read it again, it says right there in square metres.

Isn’t it strange to mesure this in surface rather than volume?

The authorities are saying they don't want to see any trash at all, regardless of volume. Imagine 100 sheets of paper vs 100 AA batteries. The batteries have much more volume, but the sheets of paper cover a much larger area so there's much more visible trash.

Not much difference between a 12" and a 18" lag bolt for the purpose of "how much trash is visible and impacts terrain".

Surface feels a bit fairer in that sense. Or at least, easier to measure.

I fairly obviously meant outside of this specific instance, if pollution etc were policed and responded to in such a manner.

This is driven in part by regulatory pressure.