You aren't wrong, there are indeed satellite branches of WDI at each of the resort locations.
That said, most of those branches aren't of tremendous significance, in terms of major decisions made, or the kind of decisions we mostly care about on these forums. Anything major or large scale, such as Pandora or a potential Cars Land (or even the Jungle Cruise restaurant), would be planned or decided in Glendale. The Orlando branch mostly consists of people that work on projects requiring intimate familiarity with a site or constant site visits — the fence additions at the resort pools, perhaps. Guardrails, Benches, things like that; maybe a small refurb or new bathroom here or there. Larger refurbs (like Maelstrom -> Frozen) are still designed in Glendale.
(Criticism time)
The problem with this centralized/remote decision-making, as some have mentioned, is that there ends up being a lack of familiarity with the park being worked on. Glendale WDI constantly shifts Imagineers back and forth depending on how projects open up and where staffing is needed.
So you're a Glendale Imagineer who just wrapped up his project for Hong Kong, and now an Animal Kingdom project opened up. You're put on Animal Kingdom now. Have you ever even been to Animal Kingdom? Maybe not. Doesn't matter really, many of the people you're working with haven't. Or you just helped finish Tokyo's Frozen land and Frozen-Maelstrom still needs work, so you're transferred to the Epcot project. Okay, so you've never actually been to Epcot, but it's still Frozen, right? Big difference.*
Well, yes it is. This is how nuances of places get lost. There is no sense by many Imagineers of what the special quirks or characteristics of the original Norway pavilion consist of, or even necessarily why the Norway pavilion matters at all (vs. just being another "Frozen project.") This is how differences that make coast-to-coast attractions unique slowly blend together and disappear.
Note: This doesn't always happen though; many Imagineers do their research, or someone will speak up about why a certain thing matters, etc. But not always. Often those people aren't in the right decision to call those shots, people are ignored while decisions are made, so on. And those more experienced Imagineers are constantly retiring or *ahem* otherwise leaving.
*Everyone sure knows Disneyland though; that maingate makes it a great weekend hangout. And as a result, everyone wants to work on Disneyland too — imagine being able to do your site visit and be back home by 6pm instead of having to fly overseas for a week.