Well, FAA to the rescue(?) again...
https://www.flightglobal.com/safety/...158236.article
US regulators are formally seeking comment on proposed fire-safety conditions to accept the large aft centre fuel-tank design for Airbus’s long-range A321XLR twinjet.
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But the US FAA is concerned that the tank’s location and design means it is directly exposed to potential post-crash ground fuel-fed fires, unlike centre wing tanks or optional auxiliary centre tanks.