It's the same rule. The Old Testament saints were saved by grace through faith, but their sins were not atoned until the cross. Christ paid the price for the sins of the whole world. It is by grace through faith that the effect of that atonement is made manifest.
I agree with that. Some people argue that the heroes of the Old Testament are in Hell because "Jesus wasn't born yet for them." Obviously, that is a specious argument.
You and I are on the same page with regard to grace through faith.