Wikis are written by amateurs and are notoriously inaccurate. Going by the dictionary definition, written by professionals: "Definition of AR15

: a . 223 caliber gas-operated semiautomatic rifle that is essentially a civilian version of the M16"

https://www.merriam-webster.com/dictionary/AR15

An M16 is an assault rifle. Ergo, an AR-15 is an assault rifle.