True you definitely can not classify Carpenters as rock music. Though one can say they are the foremost makers of "soft rock". Regardless their music was influenced by rock aritsts Beatles and Beach Boys. They used many instruments and styles which are used in rock music such as electric guitar, electric bass, progressive drum patterns. and first and foremost their music was made and became popular during the rock era and has also influenced many musicians and listeners in the rock era.
Not everyone in the RRHOF performed rock music. Certainly can't classify Mahalia Jackson or Dinah Washington as rock - not even close to it.