He said his Shikai right... Ruri'iro Kujaku is the real name, Fuji Kujaku is the fake name he uses when he wants to keep shit secret.
I'm guessing he used Kido for the same reason he unleashed his true Shikai, even though there are plenty of witnesses. He knows in a fight like this, when they're clearly outclassed holding back for any reason would be suicide. So he fell back on his real strength (Kido) and when that failed, he unleashed his Shikai... Or at least tried to before Hitsugaya kicked his ass .
I quite liked this chapter, plus that last speech by Kurotsuchi was awesome, can't wait to see what "medicines" he has to use on Hitsugaya...