It is mixing things up.
I think the purpose was more to aid freshman, but reality is different.

Redshirt freshmen have long been common in football. Basically a kid not yet varsity level can practice with the team for a year before he hits the field.
Back when I was a student, there was a freshman team that played before games and no freshmen were on Varsity.

Redshirt has been great for kids who might need 5 years to develop. The new rule expands on that.

Kids who are 10stars come to college thinking 3 years and then the NFL. Many guys who played 3 years in college and and many who stayed 5 are in the NFL.

Forget the NFL, some kids just want to play college and an extra year helps them achieve.

The new rule is if you don't play in more than 4 games you can "redshirt" no matter age or class.
This is good in many ways not expected.

Here at Clemson, incredible QB Bryant played 3 games, lost the starting role and decided to cancel this year and play next year on another team.

Today we learn Junior Cornell Powell might take that route. He is a receiver with 5 catches for 63 yards in 2018. He lost eligibility for a time due to academics. He is a good guy and an important part of the team. He got that cleared up, and now maybe should redshirt this season and have 2 full years left. He can practice with the team and if needed, enter a game. This year we are stocked with receivers, so best for all maybe him kicking in next year.
He could also transfer next year or the next as while he is not a starter here, few teams have a guy as good.