The Cyclone derailleurs I’m familiar with do not match your description. The pulleys are the same size. I think they’re 11T, but 10T pulleys work fine. And the dust covers are a part of the pulley-held together by the screw that holds the cage together.

If the dust covers are on the cage, they’re stuck on by hardened chain goop.

The only Suntour derailleur that I know of that has a larger lower pulley is the 2nd version of the Mountech with the 13T lower pulley.