So is the premise of this “without works” doctrine based upon the premise that one is saved by faith without substance?
No. Saved appart from works of righteousness. As scripture says. God IMPUTES the righteousness of Christ to us who are His and have been born again by grace through faith.
How one is saved, and how one of Gods children OUGHT to walk are two separate issues.
Many who reject the righteousness of Christ seek to establish their own righteousness through "many wonderful works in His name" but will be found with blemish and God never knew them.