Those made by Simpson in that link (and made by others as well) have ventilated sides. Those are 'high wind area' Type B Gas Vent Caps. The one in your photo is nothing like those - no ventilated sides, just a flat deflector above the vent opening with open top and bottom.

This is an unlisted single walled sleeve over B-vent and should be removed. They should have installed the mfrs listed roof flashing as well. This is probably technically an unlisted "shroud".

If you don't see a listing sticker on the pipe, then I recommend you write it up as suspicious and possibly unlisted for that application.

HTH,
Bob