As someone who used to regularly exploit economies of all sorts on PC servers, I can't really conceptualize how there's a single bug that effects the economies of multiple different servers (including those using scripted currency systems using flags rather than the default "gralats," if Classic actually uses that), which apparently works in some way through manipulating the upload system. The fact that this already exists on several other servers would lead me believe that isn't an actual thing, and this seems to be happening as Classic now reaches out to developers from servers that already had the system.

I also can't wrap my brain around the idea of an "unfixable exploit," but I dunno. I do know some things on Graal can't be handled at a scripting level, but the uploading system is a scripted system meaning it should be able to be fixed through proper scripting. Maybe if this was an issue with the survey rewards offers or something like that then this would make sense to me, but even then I'd be pretty confident that a real fix could be made.

I think it was probably changed for the obvious reason, which is that it gates players into needing to buy gralat packs to afford hats and other cosmetics when they're released (instead of refunding their old uploads). If that is the case, I don't understand why it isn't being said and people are instead being told to come to the forums and make vague posts surrounding the change.