Why does the Create() method of SHA-1 behave differently than that of SHA-256?

Why does SHA1Cng.Create() return a SHA1CryptoServiceProvider, while SHA256Cng.Create() returns a SHA256Managed?

If you can explain why SHA256Cng.Create was implemented to create a SHA256Managed instead of a SHA256Cng, I'd be interesting in that too. Currently, to create a SHA256Cng we need to use SHA256.Create("System.Security.Cryptography.SHA256Cng").

via Chebli Mohamed