Yeah, Freeza's transformations were definitely not common knowledge before the events on Namek -- only the members of his innermost circle were aware of such... Even Vegeta, who served under Freeza for years, was shocked by that revelation:
And Freeza, in turn, was surprised that Vegeta knew about his transformations:
All BoG and RoF do is tell us that Gods and the like were also aware of his ability to transform -- but that hardly makes it common knowledge. 👆
Originally posted by john allerdyceEh, I mean exactly what I said..? 😕
What do you mean by "gods were aware"?
At the beginning of BoG, Whis informs Beerus that a mortal had killed Freeza, and Beerus is utterly *shocked* by this information. After all, when Beerus had went to sleep a few decades prior, Freeza's closest rival in the universe was Ginyu, whose PL was still inferior by several orders of magnitude(Freeza was literally 1,000x stronger than him)... So I'm sure it would indeed come as quite a surprise to find out that in such a [relatively] short amount of time, one mortal --let alone several mortals-- had not only matched Freeza's power, but vastly exceeded it.
Anyway, when Whis showed Beerus a 'clip' of the battle, it featured SSJ Goku AND 4th form Freeza:
But Whis/Beerus were not at all surprised by Freeza's form. In fact, the only 'new' revelation was that Saiyans could transform as well.
Aside from them, Kaioshin was also aware of Freeza's transformations. That's why he was still using Freeza as a measuring stick/reference point... Even in the Boo-era:
But again: Gods knowing of Freeza's transformations certainly does not make them common knowledge. They *should* be privy to such information.