I have no idea, and I haven't read the article, but I did build a home about 8 years ago. When I did that, the builder had a video specifically about houses burning, and they said that with the insulation they use, houses burn much slower. The video actually had a side by side comparison of two houses that were built to be burned down. The one with the new insulation lasted much longer than one that didn't.
Nest burns cash faster than that.
As a NFPA 1001 Firefighter, without looking at my textbooks, I would say that is accurate. As a FF in a rural area, if we're onscene in more that 10-15 minutes, it's no longer safe to enter a new construction home, as opposed to 30 min or more in houses built prior to the 1990's.
Modern building materials (and modern furnishings) are far less dense than ones made 50 years ago. I was in a new house the other day that the cabinets were so light that you couldn't slam them if you wanted to because of the air drag.
Less density = more oxygen
more oxygen = more fire
The 8x figure apparently comes from UL.
The density is one part, but the synthetic composition of most of the fire load (contents) make it offgas more and flash over sooner. Also the lumber doesn't tend to be stickbilt with dimensional lumber any more, it's lots of engineered trusses and beams which are laminated together with flammible or meltable glues...
Actually the first time I led an interior attack team in an active structure fire, we narrowly missed going through the floor of the living room. Ironically, that was a 2x10 floor. LOL