Going back to Abel, let's see how Hebrews 11 described his faith
4 By faith Abel offered unto God a more excellent sacrifice than Cain, by which he obtained witness that he was righteous, God testifying of his gifts: and by it he being dead yet speaketh.
God did not testify of his belief, his right attitude, etc. He testified of the sacrifice he offered. Going back to the original story of what happened, look at what God spoke to Cain in Genesis 4
6And the Lord said unto Cain, Why art thou wroth? and why is thy countenance fallen?
7If thou doest well, shalt thou not be accepted? and if thou doest not well, sin lieth at the door. And unto thee shall be his desire, and thou shalt rule over him
You cannot escape what God literally told Cain. God did not tell Cain to "believe well", he told Cain to "do well", meaning do the same as Abel and bring the correct sacrifice, and Cain will be accepted just like Abel.
Faith without works was dead, until Christ came and revealed to Paul the mystery of the grace dispensation.
I totally agree with you, we are living in the BUT NOW period, yes, we are righteous by faith in Jesus's finished work alone. But there is no need to anticipate revelation and assume that must also be the case before the cross.