Tesla Cells have become a "generic trademark" for bigger cells.
At present (mid 2023), while there is a huge demand for more energy density for lithium battery, the current 18650 Cell can’t increase much on capacity. 21700 battery power density is better than 18650 batteries. With Tesla embracing these bigger Cells: we all are calling the 21700 cells like "Tesla Cells". They are just High Capacity Cells.