There are two portios of your question that I would like to address.
First of all, and more to the basic point of your question, there is absolutely no difference in field of view on an APS-C format camera (the so-called "crop" format) between an EF lens and an EF-S lens set to the same focal length. An EF 50mm lens, for example, will provide exactly the same framing, field of view, and depth of field as an EF-S lens adjusted to 50mm and set for the same aperture.
Secondly - the part I put in bold in your quote above is wrong. You do NOT have to multiply the focal length by anything. Please read the next few paragraphs to understand.
The "crop factor" has only one valid use. Here's an example: Joe took a photo of Mount Rushmore with a 35mm camera from a particular place using a 200mm lens. You want to replicate that photo with your Rebel XTi. What focal length do you need to do that from the same location that he took his photo? Divide the 200mm by 1.6 and you get the answer - 125mm. The "crop factor" is a REFERENCE between the two formats that lets you compare the field of view of particular focal lengths between the two formats.
The "crop factor" (related to using lenses essentially designed for 35mm SLR cameras) is always given assuming that the 35mm format (24x36mm) is the reference master. Something to realize, though, is that the 35mm film format is not, never has been, and never will be the "master" format against which all other camera formats are referenced. It is simply the format of the cameras that have also evolved into today's commonly used digital SLRs.
If you do not have significant experience with 35mm film SLR cameras, you can virtually forget the "crop factor". All you really need to know is that a "normal" focal length for the APS-C format is approximately 30mm. Any focal length shorter than 30mm is considered wide-angle and anything longer than 30mm is a "telephoto" (technically the wrong use of the word, but it's commonly used for a lens longer than "normal").
I hope this all helps clear up the mud.
I disagree. Photo sites and references talk in 35mm equivalencies all the time, especially at the beginner level. The 35mm FOV equivalences are very important to understand, so when you buy a 50mm lens, when you read somewhere that 50mm was a "normal" lens, you aren't surprised by why people seem so close in the viewfinder.