The four-skin sausage does have retraction shape keys, but they don't extend past the start of the glands since the glands themselves are a separate mesh and doing so would reveal a hole in the geometry
It's a bit of an older release though. All of the dicks in this pack were made when I was still using Gumroad earlier last year. (Honestly I should get around to making a new pack with my current skillset)
The one in the "literal bag of dicks" is an old pack containing two basic humanoid ones as well, but that those don't have foreskin retraction shape keys.