It doesn't...just makes a really long 1 page that won't fax, or worse on the receiving machine be shrunk to fit...
To tell you the truth, if I want to do something like that (this is in the Windows enviroment normally) I scan each page, then place the images in Adobe InDesign as I want them, finally exporting it to a PDF. Then, either print and manually fax or print to fax the document.
The confusion is there isn't auch a thing as "multi-page" tiffs. In other words, no such individual pages layered as in a word processor document. Most likely what you've done here is use some sort of M$ trickery, most likely it just auto places into an office doc. As far as I know, there isn't anything like this for Mac...though maybe if you have Word you may be able to do it.
I can't test it right now, as I had a disagreement with my Mac while installing video drivers for a Raedon card...and I can't get into either OS version, or boot off a CD (c key on ADB keyboard is dead, murphy's law-go figure!).
Anyone know/remember if there is a TWAIN import feature in Office X Word?