Gears-5 Campaign Jack question (Spoilers)

Ok so i’m really excited to play throughout the campaign on Insane in Co-Op with a maxed out Jack.

But if i start a new game , my Jack goes back to zero?

If i go back within my saved files , Jack goes back to wherever i was when i first played through.

So what is the point of maxing out Jack only to not be given the freedom to use him?

So strange …