It's most likely improbable. Flags were usually given when the recipient would go to the front, so presenters were usually his friends, relatives, or people in his home town.
I even can't judge if it's authentic or not. Some signatures seem to be written by the same hand (it's possible also in authentic ones, though).
The two naval captains seem to really exist. 神山忠 Kamiyama Tadashi was advanced to captain in 1929, and 橋本愛次 Hashimoto Aiji was in 1935. They already retired from active service in the end of WW2.
I can't find the rest one 小野勇次郎海軍大尉 the naval lieutenant Ono Yūjirō, but judging from the information about these people, the flag would be authentic, I think.
Awesome Translation you have done. I have had this flag over 30 years,. Can not remember much on it . If I look real close ,one of the ends is burnt . Hard to photo. I know the flag is real. It all so looks like there might be some blood on it. kind of Erie. I have another flag that talks about his semi pro baseball team called the senators before the war. But never found the roster of the team.Very neat flag,And has navy signatures to. But I have letter where it came from dated 1963 from the 2nd marine division marine to the commander that he was on Tarawa about the flag going back to japan