This way you will not be able to clean the filter as well as metal particles stuck to three or four magnets on the base of the pan. Mostly these magnets are covered with metal particles and there is no more room for more. These extra particles can move around the transmission if not removed from circulation by these magnets. There is some sludge too after some years of use. Also, you will be mixing 2 litres of remaining dirty /old oil with 2 litres of new oil.
What do you plan to do with the remaining 2 litres of cvt oil left in the can.