Ichigo's asauchi is that big fat sword he started out with when Rukia gave him her powers. After he gets his powers back his zanpakuto is always in shikai mode. At least that's my opinion. You could argue his first sword was also in shikai since the shape of it changes with pretty much every arc... but before he gets his powers back he never actually met/heard/saw Zangetsu. As far as Kenpachi goes... shrug. It has never been mentioned when Kenpachi actually obtained a zanpakuto or learned how to fight etc. Apparently he was just born one day with a sword in his hand and was able to kill anyone he ever faced ever.
But yeah, Kubo makes crap up as he goes a long. Unless you've thought out a plot from beginning to end it's easy to lose track of what you said before. I doubt he thought this manga was gonna last as long as it has. Still, it wouldn't be that hard for him to look up what he wrote before and at least try to spin it for his new plot, rather than using the same name and ignoring anything written previously.
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