By that bizarre definition, if I kill a pizza delivery driver I am committing genocide against pizza delivery drivers.
It is not a bizarre definition, it is an international treaty signed and ratified by Israel and the USA and 152 other states are parties. The same definition is found in 18 USC 1091 https://www.law.cornell.edu/uscode/text/18/1091
Also: what if I kill a single Palestinian? Is that a genocide?
Do you consider Hamas a genocidal group since their founding charter mentions killing Jews worldwide? Why not?