>>SPOILER....Harry Potter did not kill Tom Riddle.?

Voldemort's own curse back-fired on himself. And it said he had to defeat him, but technically, now that i have been thinking about it, it says voldemorts curse backfired, because of the strength harry put into the expeliarmus, meaning that Voldemorts Avada Kandavra hit him, not harry's expeliearmus. Is this an opening to maybe future books? Or am i the only one to notice this? Or is it useless? SOMEBODY HELP ME!