Hatcheries sell a "Production" breed that they are calling a R.I. White the only thing they have in common with a R.I. White is that they are White.
What hatcheries are selling are a cross and most likely a cross of White Leghorn, Rhode Island Red, and New Hampshire blood at best.
The R.I. White is a very rare breed that is getting harder to find, the breed was created by crossing a Partridge Cochin, White Wyandote and a Rose Comb White Leghorn they are also a completely different breed from the R.I. Red and not a variety.
By saying "Production" R.I. White can comes in Single Comb is like saying that the "Production" Plymouth Rock can come Rose Comb.
Chris