To declare someone dead you must have the facilities to do so. Burning Man, despite having a pretty advanced medical facility (known as Rampart), does not have the facilities to do so.
Burning Man Organization (BMOrg), Pershing, and Washoe absolutely know how many people die at the event. However, a death, like most deaths in the default world, are not particularly special. To be honest, until 2018 (due to the man running into the fire during man burn), deaths and information about them were fairly private: usually the partners and the deceased's campmates were informed, but news articles and significant publicity were uncommon. There's not a lot of benefit to running around screaming "Some dude died of a heart attack last night at this camp!" People die of heart attacks all the time.
It's the third-largest city in Nevada, although only for a week. There will be some deaths, there are also births. The birth in 2025 was absolutely not the first one, but it was notable because the woman didn't know she was pregnant, and her relative unpreparedness was newsworthy. Other births were planned, delivery was private, and the mother eventually goes to Reno or another hospital to report the birth and get a formal record.