Yeah that seems like a lot of inconsistency or I am misunderstanding some shit. Government has forbidden reading of Poneglyphs, learning about history, but there are different types of poneglyphs and the RPs are only learned about after reaching Lodestar. If there was already knowledge about LT and requiring RPs to get there then there was no point in going to Lodestar.
I think the government forbidding going to the island is referring to Lodestar for the general public, the government themselves wouldnt tell of another island, the actual island, they are just warning about the precursor.
Of course the stories part is not impossible since the prophecies and things are still a part, the Kozuki are passing down the knowledge, no way other kingdoms and bloodlines didnt have something similar.
Laughtale was never known about, in fact, no one even knows Laughtale exists. Roger only knew there was another Island to venture to from acquiring the Road Poneglyphs, then decided to name it "Laughtale", it was a land that never had a name to begin with since it wasn't known about.
When Big Mom was about to be defeated, she asked if the One Piece was even real... what Roger did was give people a hint at there being a treasure that was great, but they don't know if it exists in the first place. This is why Luffy said he doesn't care if the One Piece is real or not, he'll find out for himself like everyone else.
No one knows if Laughtale exists besides the Roger Pirates, every other Pirate is just betting on it.
Don't forget that people like Bellamy laughed at Luffy for going after the One Piece. Kid killed people for having ambition to find the One Piece. Finding One Piece to many people is a myth to many people.
This is why when Whitebeard said One Piece is real, it motivated many people to go after it the same way Roger's death inspired many to become Pirates and find this "supposed" treasure that apparently exists.
Don't think the WG ever banned people from going to Lodestar Island explicitly, it seems Roger was just the first to go there, and realised that the Poneglyphs were not just some ancient rock, but rocks that held very important information. He just hinted for people to go to the ends of the world, so some Pirates may have assumed that was the Island at the end of the Log Pose, and this was Roger's plan, he was baiting people into going on this journey they otherwise probably won't have ventured on.
Something us readers also don't acknowledge the world of OP don't know what we as readers know. We readers know Poneglyph exist, the world of One Piece do not, only a few people do. The world didn't explicitly tell people do not read Poneglyph, but there is a secret law against it which is why Ohara is special, they were one of the first to discover this.
The world don't know why Nico Robin is actually being hunted for Poneglyph knowledge, they never told them she was reading Poneglyph, they made up a lie to say she destroyed 3 battleships, and she was a threat to everyone. Reason being they don't want to tell people not to explicitly to not study Poneglyphs.... it will only make them curious, so knowledge about Poneglyphs is secret knowledge.
While we know Poneglyphs studying is a crime, the world don't even know they exist. They simply kill you once they know you're studying them.
In chapter 1114, even the Celestial Dragons don't know there is such a thing called the "VOID CENTURY", they were surprised about it. Only the Gorosei and those close to Imu, and archaeologists are privy to this information.
Roger told people to go to the end of the world to find the One Piece, in essence, as there was no reason as far as we know to go to the final Island at the end of the Log Pose, Roger telling the world to do so essentially told them to pretty much go to Lodestar which is the starting point for seeking out the One Piece (all the important Poneglyph).
Rocks didn't go to Lodestar, but he probably stumbled across Poneglyphs somehow. Also, given the fact he's a D., it seems certain D. members can use Voice of All Things to understand Poneglyyph to some extent. Roger and Luffy, speculation here, but it looks like this is one of the reasons why the D. are a race that the WG want wiped out.
I suspect this is why Rocks felt some connection to them.