Is it possible to make alfredo pasta in mixed (both red and white) sauce? Is alfredo pasta the same as pasta made in white sauce? 
While I am not completely sure what texture difference you are seeing, and I would not necessarily describe store-bought butter as 'oily', I can think of a reason why the texture of homemade butter is different: air. Depending on your method, when churning butter at home, you usually incorporate some air into the butter, giving it a 'fluffier' texture. This is similar to (but less extreme than) whipped butter. A simple test to see if this is indeed the case would be to take some store-bought butter, follow the recipe I linked to above, and see whether the result is closer to your preferred texture. 