Before revision: There is less consensus as to why a 1RM is actually safer; it may be because a 1RM can be performed with a much lower risk of joint injury (due to the lower weight), but also potentially because failure occurs due to absolute inability of the muscles to perform at the attempted weight (rather than due to fatigue).
After revision: There is less consensus as to why a 10RM is actually safer; it may be because a 10RM can be performed with a much lower risk of joint injury (due to the lower weight), but also potentially because failure occurs due to absolute inability of the muscles to perform at the attempted weight (rather than due to fatigue).