Epson 3880 media type: USFA increases size over other papers!

[narikin]

is this just me or a bug in the Epson media driver:

crop+scale any image to 10.5x8, ready to print on 11x8.5" US letter size.
in photoshop>print you will see the image nicely fitting with 1/4" borders all round. Perfect.

but...

go into Epson settings page choose a FineArt paper > Ultra Smooth Fine Art paper, (MK, high quality, rear feed, etc) click ok.
Go back to Photoshop and I find that the image has expanded to overflow the paper, with uneven borders.

go back to settings, choose a different media type, like the one above USFA: Velvet Fine Art, change nothing else, and the paper now fits like it should.

what is happening? I am trying to print on Epson's Hot Press Bright White, and am supposed to use USFA, but it cannot work!

(I am on PC)

[narikin]

ok - I found that if I go to 'Printable Area' and use maximum, centered, it jumps back to how it should, but.. why the change?
how come I can use VFA media in the normal setting, but with USFA it needs stepping up to 'maximum paper' size, etc.