Conspiracies will always pop back up. That the OP was based on something other than the timeline of events was shown by inclusion of the Wheel, which was never approved.
The actual question was/is: If the technical specs were amended to make both the Epic and Turbo Putt illegal, why was the Epic grandfathered while the Turbo Putt lost its approval.
The answer is that the PDGA decided that despite the initial approval, the Turbo Putt didn't meet even the loose definition that existed before the technical specs were tightened. They basically admitted that they screwed up and did something to fix it. The Epic
DID meet the technical specs before they were tightened, so there was no screw up to fix.
Some people like the conspiracy answer better.
It seems funny to look back on, but I was pretty vocal back in the day in support of a 10% rule where the rim could only be 10% of the diameter. I got on board with that as soon as I saw the Gateway Edge/Speed Demon prototype. I wasn't the only one. There were a lot of us that looked at where the disc design was going and thought "this is out of control." A lot of us wanted the tech spec revision. I'm kinda happy with how it played out, although the rims are bigger than I would like.
Other people look at that early Quest period and think "look how interesting these discs are. The stupid PDGA took away the ability for the manufacturers to really be creative." They kinda overlook the fact that the Turbo Putt and Wheel are useless discs. If you like useless discs, the 10M Brick is still legal.