That Piltdown Man and his less fictional brethren and their descendants gave a toss about particulate matter less than 2.5 microns in diameter (or even particles twice that size)?
It's engineering humor, a silly overly precise way to say everybody likes the fire nobody likes smoke in their face. So not really funny, I guess except to engineers giggling at the absurdity of what piltdown man would do with modern specification on pollutants.
That was clearly in jest, which should be obvious if someone also read:
> Maybe not in that exact framework, but basically, (...)
Doesn't exactly require the height of media literacy to grasp I'd say. But maybe GP's comment above does, and I'm just missing their clever wordsmithing skills along with many others apparently.