Board Thread:Theories and Speculation/@comment-29033274-20160713180744/@comment-681696-20160714120928

Thekillman wrote: When Naruto tries to form a rasengan it automatically became a Bijudama. No more proof is needed.

All that proves is that Rasengan and Bijudama work in similar ways, it doesn't prove that Minato saw a Bijudama and was inspired to create the rasengan.