I disagree that OP quit. OP offered to provide notice that he would voluntarily terminate in 2 weeks (but would continue to work for that 2 weeks). Prior to the completion of that 2 weeks the employer fired OP. So, he did not voluntarily terminate. OP was involuntarily terminated.
This is not like the joke about the person who was told they were fired. He responded "you can't fire me, because I quit." Then HR said "you can't quit because I'm firing you." This joke refers to both parties trying to terminate employment at the same instant. OP and his HR are addressing terminations 2 weeks apart.
Voluntary termination is quitting, and they just accepted the notice earlier is all.