It's not an official classification. All the conferences are D1 football bowl subdivision.
The P4/G5-6 is a media creation.
G5 was a real thing in the 4 team playoff era but not because of the playoff.
The “NY6 bowls” were guaranteed to take SEC, Big Ten, big 12, ACC, and PAC 12 champ (power 5). The top ranked G5 team was guaranteed a spot in the NY6 but not the playoff. Hence G5
In the most recent playoff changes to 12, it changed from 5+one of the G5 to just top 5 regardless of league.
The big ten could be left out of the playoff, the SEC could be. Because the rules do not differentiate status of conferences.
The power 5 has become the power 4 and it’s simply vernacular. The committee differentiates conferences but in the CFP selection criteria all the conferences are equal.
It’s like calling somewhere a third world country when the second world doesn’t exist anymore.
It’s not an appropriate or accurate term anymore because the world is changed…but if someone says it people know exactly what it means.
The reason it’s 5 not 4 because if there wasn’t a guaranteed access opportunity It would open them up to lawsuits.
If they simply went top 12 it would open them up to lawsuits.
It’s all lawsuit prevention.