I mean the body can perform some pretty amazing adaptations, but it's not magic.
I'm not a huge fan of using calories as the ultimate yardstick to measure food intake, but I'll concede that as calorie intake drops far enough, there are certain thermodynamic realities that hormonal control systems simply cannot overcome and calories will rule.
If OP is still able to communicate in coherent sentences and get by without wearing a thick sweater to stay warm indoors, that suggests their body still has additional energy conserving levers it hasn't pulled yet. 😉
At the same time, I believe OP, as I've known other highly-experienced folks in the extreme extreme diet space who have found themselves in similar pickles before. And there are certainty unique medical disorders like lipedema (which I'm not suggesting the OP has mind you, just bringing up as an example), in which something has happened in which the body either can't or won't unlock what appears to be stored fat.
So while true that not everyone on a very-low calorie diet will experiencing shivering, extreme fatigue, or mental incoherence, I just have a really hard time believing that OP has both stalled under those conditions AND done so without the body having to unlock any of the extreme adaptations that I listed.