Any 18650 claiming to be over about 3500mAh is likely to be junk. Stick with brand name batteries from reputable sellers.
Rattles? Some batteries like that have been opened up and found to have a small cell inside and the cavity packed with some powder.
A battery charger doesn’t “know” what kind of cell is in it if it is multi-chemistry. It’s uses voltage. If the voltage was down below 1.5v it would think NiMh. If it was that low, it’s WAY too over discharged anyway.