1 kB is 1024 B. It's measurement unit thing. Not logics. 8 bits in a byte. Not 10, neither 6 nor 5. Just 8.
Like feet in yards, inches in feet, meters in kilometers and ounces in pounds.
It's 1024. Period.
Then of course you are free to count as many bytes as you want and call that bunch a kB.
Pretending anyone else will agree on that is a different thing.