It's obvious that NOBODY in Konoha actually knew about this. If they did, I don't think they'd have left the souls of their most exalted leaders to rot inside the stomach of a ghost for all this time.
They did say it was an Uzumaki shrine, so the Death God seal is probably an ancient Uzimaki sealing technique or something. I don't remember if they said Minato created the Death God seal or not, but it seems obvious that he learned it by researching the techniques of his wife's clan.
The scroll with the unsealing technique is probably a relic Oro or Kabuto found in some ancient Uzumaki ruins.
Well, they did have that weird sensory bubble surrounding the village during the Invasion of Pain arc.
But this shrine might not have even been inside that bubble, given that it was apparently far enough outside the village that it wasn't leveled when Pain destroyed the entire city the way the Uchiha shrine was.
Speaking of which, they sure did a good job of building Konoha back into the same jumbled mess it was before being destroyed in a hurry. I know Sasuke says it's all different, but it sure doesn't look that way.