MiceChat isn't the most reliable source. Not saying they are wrong this time, but they generally report things and speculate things that are usually wrong.
I'm afraid you don't understand how reliable Miceage Updates actually are. Historically, going back to the late 1990's when they were the D-I-G and I read the rumors via a 56K dial-up modem, Al Lutz and his team have always had the biggest scoops and the most shocking rumors that become true. And critics, particularly those who own websites that don't get the juicy rumors first, always say Miceage isn't reliable. It is. Very reliable.
This Frozen rumor that Miceage broke back in August, when absolutely no one else was talking about it or knew about it, is only the latest in a long string of major scoops and rumors that Al Lutz/Miceage have gotten right in the last 15 years.
Like I said, the attraction is old. Plus, the majority of visitors to Disneyland are locals as opposed to WDW which are tourists (that's why seasonal activities such as the Nightmare Before Christmas Haunted Mansion and Jingle Cruise happen in LA and not FL) so how often are locals going to see the same 3D film?
That's also a gross overstatement and fundamentally flawed argument. There are millions and millions of overseas and domestic tourists at Disneyland every year. It's kind of a famous place. They don't do seasonal overlays in WDW because TDO is notoriously cheap. Jingle Cruise is also cheap, so WDW got it.
People still watch MuppetVision at DHS because it's in a theme park that has a embarrassingly low amount of attractions; only five (5) rides and a half dozen theater shows mostly dating from the 1990's. DHS crowds are desperate for entertainment, so they shuffle in to MuppetVision after they've already been on their five rides. At DCA, MuppetVision is in a park with more rides/attractions than DHS and DAK combined. DCA has 25 rides, plus a half dozen theater shows that are actually good and from this century. There's so much to do at DCA that it's easy to skip MuppetVision. Very easy.
And finally, Disneyland is in Anaheim, not Los Angeles.