I'm not sure I follow your argument. We'll have to wait, but the story is we are boarding Tiana Food's log-based transportation system? I'm not seeing how a flume ride system relates to a New Orleans-based food production facility in the Louisiana salt mines.
You're right, we don't yet know what (if anything) they'll offer as an explanation for the logs. But my point is that like many other attractions, the story has a layer of "a business that has settled into this place (the office, the business operations, the crops we see, etc.) and guides you though the environment."
My guess is that the story is Tiana's business uses the old salt mine's rivers/canals to move product from the bakery/kitchen to town. Like
@Disney Analyst posted above, they could float cargo down the river. This would fit with the "crates of beignets" we've been told about (and explain why beignets are in crates!), and would explain the use of logs as transportation for guests from the factory/kitchen/farm business out into the bayou.
I totally agree that in each of the other attractions, the "office" creates the setting for the attraction. We then go into a secondary story - but still within that setting. I just don't think it works that well because the story we have so far involves too many things (a food production company in the Louisiana salt mines, a New Orleans party and a bayou adventure in a magical area of some type). Not saying it couldn't be done. It's just not the straightforward/consistent story each of your examples have.
Pandora has layers like this. The land is set a couple of generations after the film series.
"In the Valley of Mo'ara, nature has been steadily reclaiming the Resources Development Association's (RDA's) old facilities and relationships between the humans and the Na'vi have become much more friendly. A new eco-tourism group, Alpha Centauri Expeditions, or ACE for short, has established a treaty with the Omaticaya tribe to establish a base camp for human tourists to visit Pandora and share in the Na'vi culture. Additionally, a scientific group known as the Pandora Conservation Initiative (PCI) has been working with ACE in helping restore the damage wrought on the environment by RDA's operations and have taken over the Avatar program to allow guests to fly on Banshees."
Is this any less convoluted? But it's all needed to make sense of how guests are able to visit Pandora, why there isn't an army of mercenaries like in the film, why Na'vi and humans are friends now, and why scientists would make it possible for us to use Avatars to ride banshees.