It's all very subjective. I've barely noticed Johnson saying that, probably because he says it about everything, it's just noise.
However, it's could easily be argued that Johnson was the first Western leader to take a hard line against Putin and that paved the way for everyone else. Diplomatically he was first and I think that's reflected in the praise he's receives from Zelensky.
But either way, even if I'm horribly wrong, it's just nitpicking. We're 2nd to the USA, a good performance and really not worth worrying about a bit of loose talk from Johnson.
I agree with most of your points. But in some areas, what Johnson said and what he did, didn’t marry up. He said he was taking a hardline on Putin but wavered over sanctions, with very flimsy arrangements that gave Oligarchs that he is clearly in bed with, time to move assets. Johnson was never going to section Russians harshly. They fund him.
It’s almost as if Johnson wasn’t telling the truth.