Actually the article I saw at the time Tieskoetter stated:
"Yes! All of the templates we ship with Lightroom are made using Illustrator, and I'll be documenting the process for creating those. We've also successfully made templates using InDesign and the freeware tool called Scribus, so if you need templates in different sizes, you'll have a range of options."
Unfortunately, that documentation was never shared with end users and Julie Kmoch later offered:
"Sorry, but we've decided that the approach we were originally pursuing to create custom page layouts was not something we were comfortable releasing to the public. The scripts we've built have worked well enough for our internal use but needed a lot of work before they were usable without a lot of guidance. We think it's more prudent for us to focus on enhancing the book module itself."
In other words they changed their mind so they could focus on making the Book module better for Blurb ... and it only took another 6 years to be at a point where Adobe can now boast about "greater flexibility to move and resize photos around a page"
Job well done!