It's almost like defences... are defences. Not random fights against whoever. It's one immensely qualified fighter attempting to beat you after the other until you fail to beat one. By your logic Jon would be at 14 defences. And he certainly has the far greater argument to go with that standard as his 14 fights have all actually been title fights, just sometimes he was winning the belt.
Not withstanding the fact that not every fight Fedor fought after winning the belt remotely even deserved to be a title fight (as opposed to presenting it as 18 wins over the best), Pride didn't like designating title fights for their champs because they didn't want them losing their belt. They'd rather they lose but can still be promoted as champ for another fight. Which proved well thought out as that's the same fuckery WAMMA pulled after Werdum tapped Fedor in 60 seconds. The fight had been promoted as a defence for Fedor and then when Fedor lost the belt wasn't given to Werdum, and just magically disappeared.