Createspace spine width error message (and how to fix it)

If you’re designing a full print book cover for Createspace, the spine width needs to be calculated based on the final page count. Here’s the formula.
For a 6″x9″ book, the height will always be 9.25″ and the width will beĀ 12.25″ plus the spine.

For black and white-interior books:
White paper: multiply page count by 0.002252
Cream paper: multiply page count by 0.0025

Example calculation at 6″ x 9″ cover with 60 B&W pages on white paper: 0.125″ + 6″ + 0.135″ + 6″ + .125″ = 12.385″
The problem with this is Createspace’s automatic checking system is overzealous. All the text on the spine has to have extra padding, or you’ll get this message:
“The spine content was too large for the page count so we reduced the size and centered it, ensuring that there is at least 0.0625″ of room on either side to prevent the content from wrapping onto the front or back cover when printed.”
And in January of 2014, suddenly all my clients were getting this message, even though I used Createspace’s formula and did everything right. I already knew that for very thick books, over 500 pages, the spine is often going to be off because of slight variances in the paper.
But for smaller books, there’s not reason for Createspace to automatically be resizing my spine without permission.
For a few projects, we got in touch with customer support to figure out what was happening (and to ask them not to mess with our cover design) and the service rep said that actually, the “fixed” file was the same as our original file.
Which sounds like a Createspace autovetter problem, such as they immediately flag every project as “wrong” and then “fix it” even if the difference is infinitesimal.
The problem can be avoided, a little, if you use wraparound art so there isn’t a clear break on each side of the spine, and by making all the spine text extra small.
This isn’t a great solution, however, because “normal” or traditionally published books often have large spine text that extends to the very edge of the spine (or even wraps around the spine a little).
Createspace’s system is a pain in the ass if you have lovely, large, script fonts with long loops or tails – you have to squish them together or cut the ends of the fonts off so they don’t go out of bonds.
I understand Createspace is trying to protect non-designers from screwing up their books on accident, but their design constraints make it difficult for cover designers to make beautiful covers – and then they send out arbitrarily error messages that needlessly worry clients (I almost always have to tell them, contact customer support, or just order a copy and check the real version).
This isn’t to say I’m flawless; I make mistakes sometimes, and it’s nice of Createspace to warn us if something has gone wrong. But I don’t think I’m so entirely off my game this month that I’m repeatedly screwing everybody’s spine width up, over and over, through multiple corrections.
Something has gone haywire with Createspace’s spine-checking system.