Yes, AA uses the term "overmatting" to describe both types of window treatments, only in the sense that he doesn't specifically mention other print mounting techniques other than dry mounting (on the page you reference). I would only suggest that the term may have undergone some degree of evolution, and that using one or the other is only important insofar as those who are interested in your work are able to distinguish how your prints are actually presented.
For me, overmatting speaks specifically to the window covering the actual printing paper, a method which normally accompanies hinge or other non permanent mounting schemes. The physical attribute of such is that the window overmat assists in holding (the edges of) the otherwise loose print to its back or mount board. Many photographers do this successfully on relatively small (<=20"x24") papers. By printing with an adequate margin, the print may be signed right on the (white) paper margin with room to be reasonably held down by the overmat.
Dry mounting (as you know) is a mostly permanent mounting technique, decidedly not appreciated by all, which results in a smooth professional look, when done well. The print does not need to be held down and so may be separated entirely from its window as in a portfolio, without fear of catching a corner or side of a loosely attached print. The print may be "floated" (the other term) within and entirely separate from the its window.
The aesthetic and artistic value of floating a window over a suitable dry mount, as opposed to overmatting, so defined, is that the artist decides the ultimate frame of the printed photograph, not a framer or curator, who must cover the margins of a print with a window to display it once the window (if it ever existed) becomes separated from it. There is an unfortunate trend among museum curators (who prefer "loose" prints) to overmat vintage photographs into the image area, which does not honor the vision of the artist. I see this all the time at the Getty (LA), where some way of presenting loose historic prints must be devised. But last year I also observed it on a dry mounted Adams print, cutting into the actual image area. I don't believe the artist would have been at all pleased with the treatment of his work of art.
Of course you may link to my site.
Last edited by ROL; 10-12-2012 at 08:29 PM. Click to view previous post history.