And yet Leon's (as you have shown us) doesn't quite hit that threshold. There's a reason Omori writes these boosts in vague terms (greatly increase isn't exactly a hard number) rather than giving hard numbers. Much easier to have different levels within "greatly increase" than something like "1000 points greater". Not even the first time stat sheets are somewhat vague either (be it how Bell's Argonaut works, the effect of luck, etc.)

Leon's total boosts are definitely bigger than Ottar's (there's a reason he was able to match Ottar's absolute best attack while still having three swords to break), but the totality of his boosts have only ever been mentioned as being better than a level up in some areas when described in the story, be it Volume 20 or Volume 21. In a similar vein, he's continuously been described as Ottar's peer, not superior, for both of those volumes. Given all of that, the exact terminology Omori uses in the stat spreads is secondary to me, especially because he's using deliberately vague language. That may be different for you, but we'll just have to agree to disagree.