What are Yu an idiot or a moron? to be in Bijuu mode, you must have a Bijuu inside of you not the chakra. Minato is using Kyubi chakra mode just like Naruto before befriended kurama.
OMg thank you thats like ginkaku and kinkaku have chakra cloaks of kurama. It's known as Psuedo-jinchuriki cloak a cloak thats a mixture of the KCM and BM of naruto uzumaki