So, the new Chi-Nu from battlepass is unavailable for the tech tree Chi-Nu squad.
In-game, the tech tree Chi-Nu is a rank IV unlock with Tanker III squad, called the 10th armored regiment. But it could also be used with the previous tanker Tanker II squad - the 1st armored regiment.
With the battlepass came the new skin version of this tank. The problem is that it is only usable with Tanker II squad. Since the tech tree version is unlocked with Tanker III squad, the new battlepass version should also be usable with both squads.
Made an album that shows all possible combinations together with the last picture where you can see, that you cannot use battlepass version in the Tanker III squad. (I also made sure it’s not because of the “Busy with another squad” game mechanic).