A good rule of thumb is that any player that has a sig amp generally does not get their iconic tone from said amp. It's a chicken and an egg problem. Person with tons of talent takes a good piece of gear makes some classic music with it, wannabes want "that" sound, after several records, tours, negotiations, manufacturing details, etc, etc, the hype machine starts pumping out sig gear that is essentially trying to get the tone of a hand selected or modified version of something that already exists in the wild; if the artist uses it their tone changes, if they don't use it people feel ripped, it's lose/lose much of the time.
At least Eddie used the 5150 but anyone buying one hoping for instant brown sound was bummed. How many signature amps did Dimebag have? I lost count... Dimebag tone still == a correct era Randall RG100ES and an EQ.