True the SO6P was a legend for everyone, but it was never mentioned that SO6P even fought the 10 tails in the legend if you read the manga correctly , nor was it stated that the SO6P was a Jinchuuiki.
I'm pretty sure everyone noticed the beast, but let me ask you think did anyone ever try before Hashirama went and captured all of them?....No they didn't so that wouldn't change now.
4KK wouldn't be able to take Shukaku as himself because Shukaku could take him out with air bullets or TBB, plus where would he get the idea fo Jinchuuiki if Hashirama and Mito never did it?
So ounce again No and also the G&S brothers doesn't make any since to me and hear me out because it won't make any since to you either after I explain. Hashirama captured Kurama and sealed him inside of Mito before the first great ninja war and yet some how, during the first great ninja war after they betrayed their village they ran into Kurama in the wild and got eaten by him?
I do not mean his generation but the entire Narutoverse
-4KK could control Shakaku sooner or later
-Randome ninja would still try to get their power or die trying or almost die and get some power
-Kumo was also a village that tried constatnly to steal bijju like Kurama
-Sooner or later people would pick up the idea of jinjuriki
-Oro may make some evil experient
-Rogue Uchiha could control it
-using S06P tools to control it
So your saying Nobody else in the narutverse could control the bijju ??
1-The Anbu would jsut act sneakier
2-Tobirama would say they are lying and sides would be taken
3-Thus starting a civil war in Konoha
4-The village would be tense! Who knows who is watching who and who is to trust
5-Talking about Tobirama's spies would ruin their chances for a Coup de ta
The point is Tobirama made few more (bigger) few mistakes than Hashirama's few mistakes
They work on getting fair treatment peacefully without risking the possibility of getting themselves killed over something they did. It's been made public so the people that did believe would watch to see if it was true and either one of two things would happen, either Tobirama would have been forced to stop out of fear of being caught in the act or he would have been caught in the act by the people that did believe them who would then tell their clans that what the Uchiha said was true and now that they had people with proof ro back them up, people would have no choice but to listen and force Tobirama to stop anyway. Because the Uchiha is one thing, but all these other clans couldn't possibly be lying to start trouble.