Disney never tried hiding that Splash was based on Song of the South. Song of the South is written on the Riverboat in the finale, and they even used to say the ride was based on Song of the South in the ride description on the Disneyland App. They also mentioned it was based on SOTS during The Imagineering Story.
They may not have directly hidden the ride’s tie to the film, but I don’t think they wanted to necessarily promote the film either, for obvious reasons.
As I’ve stated before, Disney is completely at fault for what’s happening with Splash.