I don't see why we shouldn't take the SOULs book and its translation (and according to the diverse translations the wonderful people here did, the meaning it pretty clear) as serious official "proof" because... It's not something coming out of the blue. Many people (mostly IchiRuki fans but also neutral readers) have interpreted this scene the same way than the SOULs writer. I wasn't a big shipper when I read this part, but it's how I interpreted it too (and thus, it fed my IchiRuki love).

As for Kubo and how much he has to do with it, since he seems pretty involved in all things Bleach (doing anime/movie designs) and he insisted in the importance of catching the meaning of a panel, I'll believe he validated this interpretation.

Oh and I seriously don't think it could be Orihime imagining things...really. Because such a big painful and serious moment? Not meant to be misguiding, especially since there are precedents. When Orihime mistook Ishida sewing a dress for Rukia as him being in love, it was totally comical.