Is a valuation realized by prestigious investment bank a scientifically approved result which any investor could use as a reference?

No. It neither is scientifically approved, nor valid for any investor. A valuation is just an opinion

Thanks for invitation,

Of course, the scientific and up-to-date evaluation that conducted by any respectable investment bank could be an excellent guide or  reference than can help any investor who are willing to be familiar with the economical and investment trends in general.