I'm a little fuzzy on how score damage changed this, but once upon a time:

protection = 25% dam redux. So that was vuln applied first, and then 25% reduced damage.

Resists = 33% resist but also negated vulns. So a theoretical resist metal prep would have negated vuln + 33% dam redux on top of it.

These days, I guess it doesn't erase the vuln anymore? No idea. Could probably try a resist fire prep and score damage command to figure it out.

Sportsmanship killed CF