I don't know about Smashwords, but Draft2Digital is great when it comes to dealing with Apple. On Tuesday I republished a book that Apple had rejected because I referred to the iBookstore rather than the required iBooks Store, plus one dead link.
On Wednesday, I got a second rejection by Apple for the identical reasons. I emailed D2D to point out that they had been corrected.
On Thusday, I got a reply from D2D confirming that they'd checked the epub and found that I had indeed fixed the errors, and they would go back to Apple for more information.
And on Friday, I got the form email stating that the book was live on the Apple store (or should I saw iBooks Store?), and indeed it is.
I suspect that Apple's real problem with the book is that it mentions Amazon in the title:
https://itunes.apple.com/us/book/id948746747