They absolutely are not the same. Renji doesn’t even know the name of his true Bankai. Ichigo knows the name of his true Bankai. The only person who understands the Blade Is Me is Ichigo, and maybe Aizen. Renji does not understand his own powers near the degree Ichigo does.
But then later it's also flat out stated the reason Zabimaru lied to Renji was specifically because it didn't aknowledge his strength. Only after the training was virtually complete did Ichibe tell Renji its real name.
Are we then now to assume as well, using that post-gatonden Renji scaling to Ichigo, that Zabimaru would (hypothetically) also refuse to aknowledge Ichigo's strength at that point? The guy who fought almost toe to toe with base Yhwach? It just doesn't quite add up to me, narratively speaking...
I also think we shouldn't conflate "understanding their own powers" with "understanding who they even are". Sure, the 2 things are connected in the Bleach verse, but I wouldn't say they're the exact same.
Again, the Asauchi challenge is heavily implied by Ohetsu not to test the individual's strength or how much they understand their power ('cause during the challenge they're not even using their zampakuto (their power), they're both broken and unusable). The test is instead implied to test their conviction in themselves/their own identity - it's the whole reason Ohetsu sent Ichigo away to find himself in the first place, and why he aced the test once he returned.
It makes sense for Ichigo to lose that first time, since he was at a mentally vulnerable place at the time, at a point of low confidence - he was still grappling with Yhwach's comment about his mother.
Idk... contextually, I personally think this interpretation makes more sense.
Hmmmm...
What if we say the post-gatonden Ichigo who got bodied by the Asauchi was not only physically nerfed (like Renji - unusable zampakuto), but also mentally nerfed by his crisis of identity? In this case I think it wouldn't be that crazy for him to have dropped down to post-gantonden Renji's level or below, momentarily...
Emotional amps and nerfs are also a common occurance in Bleach too, so this wouldn't be too out of place, I suppose?
What do you think?