My suspicion is that the went to solid bottle shelves to eliminate production cost, and there were less moving parts to have make and stock!
Of course this is only my opinion!
My guess too. Over engineered to provide a high level of reliabilty. Either way I will try (eventualy) to get a full set of original 81 shelves for my machine, but until then I will most likely use 63 shelves to keep
my "poduction costs" down