Surely you can see the damage this would do to the majority of children currently being told they are "gifted"?
Being "gifted" until the 6th, 7th, or 8th grade would psychologically cripple a lot of these kids through high school. It's better to not allow that "advanced but not gifted" demographic in from the outset, than it is to unceremoniously boot them at some arbitrary time in the future if they fail to keep up with those at the extremes.
The better ideas are the remediation, normal, advanced and then gifted classifications. And you don't get the gifted label unless you are on the extreme of exceptional.