There is far far more in terms of containment in the nuke plant, but, the stuff inside is much more dangerous and longer lasting.
This is pretty much a worst-case scenario for battery fire size and spreading. It is a very early large-scale battery deployment with what appears to be completely insufficient fire suppression, and very little thought for fire isolation. It was a tightly packed indoor multi-story facility, very unlike the more typical outdoor shipping-container style facility.
[1] https://www.readymontereycounty.org/emergency/2025-moss-land...
[2] https://santacruzlocal.org/2025/05/15/new-soil-tests-start-a...
https://www.countyofmonterey.gov/home/showdocument?id=139505
Metallic taste in the air was the worst symptom that people reported, and people here were complaining of metallic taste in the air, 40 miles away, upwind from the site, for months. So unless something really shocking comes up in the report this month I think battery fires are mostly a concern for insurance companies and fire code to protect fire fighters and other structures. IMHO building below grade and dumping dirt seems to be massive overkill; just separate containers and don't stack them so that a lower fire spreads to multiple upper containers, and things are probably fine.