No, from my understanding the GECK they released is definitely not the same platform they used to make the game. It is very much scaled down. Unless you thing the Devs them self have to come up with strange ways to get around the hardcoding they apparently didn't put in themselves.

If we're using the same GECK why can't we change those very settings?
Because you're talking about two totally different processes.
The designers work with the same GECK we do, with all the same hardcoded functions we have. If they want something to change, they need to apply to the programmers for a new scripting function in the GECK. That's why each time something comes out with a new function, we get a new update for the game - and normally a new GECK to go with it. Remember they updated the GECK after the DLCs came out?
They get the new GECK with the new features so that the designers can make the game; then we get that GECK with those features so we can use them.
The only Key difference between the GECK we get to play with and the GECK that Bethesda (and I'm sure Obsidian) use is Version Control. We know for a fact based on records and broken references that the GECK was actually built to work with some kind of version control system (if its not built right in). This allows a large team of people to work on the same content - which is Not something that Bethesda would want to release to the public. Its really a touch of strategic genius in my view, that Bethesda realized that they could release the GECK with nearly all features turned on - just so long as the Version Control wasn't enabled. Without version control, it is extremely difficult for a team of modders to work on the exact same content - and it would be Impossible to do so had ElminsterEU not developed Fo3Edit (which I'm sure Bethesda didn't count on). Even so Fo3Edit is not a version control system, and its not built-into the GECK. This is the touch of genius - Beth was safe in releasing their best game-building technology, fully knowing that without version control, it would be pretty much impossible for another Group to build as fast as they can with version control built right into the GECK.
Ummmm ... I'm really not thinking there's any "strategic brilliance" at work here. As you said, FO3Edit provided a workaround so their evil plan was quickly foiled; just as TES4Edit and MWEdit opened up functions in previous games. I do seem to recall devs saying on the forums before that our fan-made workarounds are often more user-friendly than the ones they use themselves. I would find it far easier to believe that they're using their own FO3Edit that's not as good as Elminster's, which is why they never bothered to release it. Have you noticed how none of the DLCs interact with each other? You'd think that they'd do that if they could - they're clearly bound by the same limitations we are. I remember very clearly the conspiracy theories surrounding the broken lipsync function in Oblivion and the howling that it had been disabled because the devs were threatened by the skills of the modders. None of that took into account how out of all the Oblivion DLCs, only SI and KOTN had new dialogue - none of the others had any spoken lines, which rather confirmed they were in the same boat as the rest of us.
Having multiple people working on a mod at the same time wouldn't even make much of a difference anyway - taking the Lokken Mountain example again, Teutonic made the island and then Emma made the mod - a full 30-hour quest with hundreds of NPCs and thousands of lines of dialogue - entirely alone. Hell, even I could knock up a substantial landmass (200+ cells), over 300 NPCs and several hours of quests all on my own. Sure, it took a couple of years, but people were still playing the game. I don't think anyone decided not to buy an expansion because of my mod or anyone else's mod. I haven't heard of one lost sale of Bloodmoon because of Wizards' Islands, even though that introduced snow even before Bloodmoon did.
The thought that mods somehow act in competition to DLC/game sales becomes even less persuasive when you look at the ratio of PC sales to other platforms - it's a small minority, ergo most players
cannot use any mods at all. Of those, only a fraction do use mods, and even fewer make them.
Yes, it's a terrifically fun hobby and I really enjoy using and making mods - but I'm struggling to see any link between my unquestionable genius at creating pink rugs in the living room, and anyone being talked out of buying New Vegas.