That doesn't show she's not Grade 1 at all. That just shows she thinks Nanami is the ideal/standard for Grade 1 Sorcerers. And Nanami
is. He is an exceptional Grade 1 Sorcerer. There are obviously variances in ability between Grade 1 Sorcerers. "So this is what it means" means she is epitomizing him, seeing him as a gold standard for people of that level. Not implying she's not Grade 1 when she was literally recommended to be Grade 1 herself.
Uh, notice how the scan also says Nobara was weakened too. And this doesn't matter unless you can quantify how weakened Kechizu was, because there is no reason he should be weaker than a Semi-Grade 2 Curse when he himself is a Special Grade Curse. ESO doubted her, but his judgement isn't final. He was clearly wrong, because Nobara proceeded to kill him. He
also believed Yuji wouldn't kill him before he could do something about it, and that he wouldn't drop his ability. But he ended up being wrong.
And what's funny is in your scan, the REASON he believed she couldn't kill Eso was because
she was weakend
Quoting it: "But can that girl kill my brother
in that condition?"
Him questioning her ability, and then being wrong about all the assumptions he made isn't evidence she's below Eso's level. Not by any meaningful amount anyways.
Nobara never actually harms Kechizu at full power, only harming a weakened version of him with a Black Flash, and then an even weaker Kechizu dies to hairpin, which we rate as higher than her normal A.P already. Nobara planning on fighting Eso doesn't mean much on its own, especially when she figured she could take out Haruta and failed, and then tried to fight Mahito and failed
That same weakened Kechizu takes hits from Yuji. Which is why I specifically sent Kechizu eating hits from Yuji when he was weakened. Not him eating hit from Yuji BEFORE being weakened. Nobara was also greatly weakened. And you can't quantify how weakened they are, so it doesn't really matter much. It evens out. Nobara planning to take on Eso does mean much, because it means after feeling his strength, and sensing his Cursed Energy, she was confident of being able to handle him in a 1v1. Not to mention she was still confident she could kill him after hitting him across the back of his head and feeling how tough he was.
She
could have taken out Haruta. She wasn't aware of his technique, which is what was allowing him to win over her, because it grants him supernatural luck. Making him both unkillable while it's active, but also land his attacks with super accurate precision to weaken her.
She also didn't fail to fight Mahito. She beat the clone of Mahito it had to run away. And then the real one touched her across the face
specifically because she let her guard down as stated by narration because she thought it was the clone who couldn't use Idle Transfiguration.
While I'm fine personally if Nobara isn't listed as 8-B, she should scale above the Semi-Grade 2 Curse for being able to take on a Special Grade Curse, and recommended to Grade 1 by other Grade 1 Sorcerers. Weakened or not, she TOO was weakened so that evens it out, and the fact you can't quantify how weakened he was means we have no reason to assume he was weaker than a Curse 4 Grades below him.
But I will say this; I think Nobara should be street level physically, and scale to a tangible tier with her nails. Not just "higher". Even if you don't for some weird reason want to scale her relative to someone she beat under equal conditions, her nails have their own feats like blowing trees up against Momo and blowing up the head of concrete Curses, etc. Which can ofc be calculated.
