The battery heats itself in these failure modes.

Not to 300 Celsius degrees.

A battery of any kind can overheat with the output shorted or during excessive overcharging, but normally whenever a battery is used in a device there are protective devices that prevent such events.

If there are no protections, the designer is guilty, not the battery. Moreover, such risks are greater for Li-ion batteries, which have flammable electrolyte.

Na-ion batteries will replace Li-ion only in certain applications, like stationary energy storage, cars for cold climates and cheaper cars, while Li-ion will remain the choice for maximum energy per kilogram.

But it is weird to be concerned about the safety of Na-ion when that is certainly not worse than for Li-ion and most likely it is better.