If Yamato joins it goes completely against the themes of the Straw Hat crew. They’re not a group that went out to sea purely because they wanted to be a pirate. They went out with the intent to accomplish a dream. Yamato has no dream no narrative and nothing.
I will take that as Wamato's will is so strong it breaks the narrative
When did Zoro say that?
Zoro and Kaido clearly fought 1v1 in that moment. No one interfered and Zoro was on his last legs. He could have a CQC bout with Kaido, and land the first blow before collapsing. And Kaido was not holding back. He was pissed off and was trying to kill Luffy.
It impossible for Zoro to be YC1 level. Absolutely nothing suggests otherwise. Zoro without using his full power(Asura) made short work of King after learning ACOC.
Nothing says Kidd and Law are far stronger than Zoro. Zoro and Law took out Mingo's top officers in similar ways, both escape Fuji's gravity, both sensed Carrot at the same time etc. On the rooftop, Zoro was taken more seriously than Law, and Law himself had jaw drop at Zoro's tenacity.
I highly doubt 2 laws or 2 Kidds can beat Kaido when they were no match for BM despite having plot on their side. Her being too strong was why they went for a ring out in the first place.
Pre-ACOC Zoro said he wished he could have at least knocked Kaido off his feet
Roc gun did that, although without the hybrid form maybe? I'm not sure
So base Luffy did what pre-ACOC Zoro wished he could
Zoro fought Kaido alone, for a few seconds
Kaido was holding back a lot because the story keeps repeating throught the battle with Luffy, that his haki is getting stronger
So Kaido was just playing around
Wano ACOC Zoro is YC1 level because he was matched by YC1 King, that's what makes him YC1
What says Kid and Law are a lot stronger than Zoro is this:
Wano Zoro is YC1
We see from the first round of Luffy vs Kaido, that Kaido one shots YC1s
We know from Kaido's spars with Big Mom that he and her are pretty equal
Kid and Law took many hits from Big Mom, and defeated her
Zoro was YC1, so two Wano Zoros get two shot
Assuming Kid and Law are around equal, two Kids or two Laws defeat Big Mom, which means they defeat Kaido
So Kid and Law are a lot stronger than Zoro
Personally I now put Zoro and Sanji at YC+ because they got stronger from Wano to Egghead and from Egghead to Elbaf