There's the reason they used the larger wood.Since you are not stacking boxes you may be able to adjust inside height at top and bottom to give bee space. A 1×10 is only 9 1/4 inches wide so you need additional space above and below.
Thank ya'll for the answers, I wasn't taken the bee space, from the bottom of the frames to the top of the base board in consideration. I got it cut out of 2x12 waiting on some sunny weather to complete.The plans I found use 2x12 lumber, would it be wrong to use 2x10 instead? The vertical hives use 1x10 for the deep.