Tell me you have never seen what happens to a human skull at those temperatures, without telling me...
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Source text:
https://link.springer.com/chapter/10.1007/978-3-031-48381-3_9
At those temperatures the soft tissue and skin undergoes a process known as Burn Scar contracture - effectively "SHINK WRAP" around the underlying skeletal structure. The object in that photo is 1. Detached - torso is missing and looks to appear out of place.
If it were explosive decapitation - you would expect to see the skull land several hundred feet away. As you can witness here in the case of this suicide bomber - the explosive blast would cause maxillofacial injuries consistent with explosive deception which are missing in the source image you have shared.
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Even in the case of severely charred human remains following vehicle explosions - the human body shows signs of burn scar contraction which are not present in the image you have shared.
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Conclusion - at a cursory glance, that image you have shared is highly, highly dubious and lacks authenticity.