[kraken]

It's only a graphic detail,

Spoiler for manga:

his new mask don't give him any new power, it's a very little incoherence. during the whole volume 24, the mask of Shawlon change every chapter and Grmmjow don't wear his mask during an entire chapter.

And Tite kubo have made worse into the last chapters. All the stuff about the Hyougoku is just so silly...
It's the same for the Visard, why are they under the illusion of Aizen.
It's forbidden to release a zanpakuto without a grave incident so Aizen couln't hypnotise the captain during turning back the pendulum or before and aizen said in the volume 19 that he hypnotised all the captains and vice captaine when he was already a captain, so when did he hypnotize the visard?.
And if they was under his illusion, Urahara and Yoruichi would be too (but, they don't seems to be).

The manga have many worse incoherence that a detail about the appearance of a mask.
The final form of Zenbonzakura have'nt the same color in the anime that in the make, but it's make no change in the story

it's the same here:Even If the mask is different, the story wouldn't. It's not as if new mask change his powers

And don't forget that in the bount arc, Ichigo was unable to use bankai during 15 episode.
We have also seen that Ichigo isn't capable to wear the new mask more than some second.
So, the anime staff can make regress Ichigo one more time until he will be able to use his new power.