It's hard to ascribe to stupidity what really looks like malice when checking out their documents: it really /really/ feels like they picked the most complicated, roundabout and confusing way to lay all that out.
Finally sitting down with a spreadsheet made the error obvious.
I feel like I should sue them on behalf of like... everyone? For making a largely unusable website with public money? The bar to clear was so low and yet you somehow failed?
The fun part of course is that this is NOT render cache, this is "Magic Mask tracking files" (roto brush, for AE folks) and it takes hours to regen so now, you absolutely cannot clear that cache.
(Unless, like me, you exported it as a matte in a separate step — I should actually do a write-up about all this)