Forgive me if I'm missing something.
I'm in utter disbelief that the printer would change your document size!
"when you print border-less the software automatically enlarges your image"...
Even if it doesn't have to? ...
The piece of information you are missing, is that it always has to. Borderless printing always involves printing larger than the paper.
In the real world nothing is perfect. An 8x10 cut sheet of paper is slightly off in size. The paper does not feed perfectly straight, and may not be positioned exactly where desired. If the printer were to attempt to print exactly 8x10 on 8x10 paper, then any misalignment or imperfections would result in a small white border on two or more sides.
The way most printers work is to print an image that is larger than the paper. The edges of the printed image are lost as they print off the edges of the paper. Losing some of the image off the edge is generally less objectionable than unwanted white borders.
Whenever you print borderless you need an image that's larger than the paper.
Some printer drivers handle this behind the scenes. If you select borderless 8x10, they scale the image up to about 8.4 by 10.4. You provide an 8 x10 image, and the printer driver handles stretching it (and resampling it) as needed. A side effect of this hidden scaling is that it invalidates any careful resampling that you may have done to prepare an image that was an exact match for the printer's resolution.
Some printer drivers offer an option to eliminate the secret scaling and just present a larger paper size. On my Epson 3880 I can select "8 x10 Borderless (Retain Size)". This presents me an 8.39 by 10.39 canvas. This option exposes the necessary overspray needed, without hiding it. I like this as it gives me the option of knowing exactly how much Image I need to get an 8 x 10.
In the traditional printing industry, this extra amount that is needed is called "bleed". It's typical for press printed pieces to be printed on larger paper, and then cut down to size.