A lot of laptops ship in a long-term battery storage mode, that you have to disable with a unique power-up procedure, the Steam Deck even has a setting in the BIOS for this that can be user enabled/disabled, and some Gigabyte laptops even have an advanced BIOS features exposed with a Konami Code have this as well. I'm wondering if this is one of those features that's in most laptop firmware but just not visible in the consumer version of the firmware, and if there's an easy way to get to it? A lot of laptops pull on the battery pretty hard even properly turned off with Windows...
In my ASUS laptop, it's called "Shipping Mode" and is readily available in the UEFI. Laptop in Shipping Mode can be only brought out of it by connecting a power source and then turning it on.