It may be that if current fire fighting assets were available back in the day, substantially less an area may have been burnt, so comparing past areas burnt with current areas in not an entirely 1-1 comparison.
Comparing area burnt from 50 years or more ago with today doesn't take into account the resources now available to fight fires. It could be that if current fire fighting assets were avialable in days gone by, far less an area may have been burnt.
Bing Mobile Friendliness Test correctly renders JS pages. Fetch as BingBot does not currently. I logged a support request through Bing Webmaster and got a reply that their engineering team is working on it, so I would expect Bing to crawl JS sites just like Google in the near future.