This isn't an amazing discovery on your part. I own the book. My 11-year-old cousin who misses Hero Factory has the book. They probably own the book. You ain't special for finding the book.
There's also the Bionicle Encyclopedias, which likely have the same pronunciation you have (I haven't checked in a while), Bionicle: the Game and the Bionicle Introspective, which use Loo-wah, and finally Bionicle: Mask of Light, the 2015 animations, and Bionicle: Journey to One, which all use Lee-wah. Since most people see the widely-broadcast visual media (approved by LEGO!) first, they go off of it.
(Note: The only sources that use Lay-wah are written by Farshtey. He didn't create Bionicle, as much as people pretend,)
We could have discussions for years about name pronunciations, and we already have, and your "discovery" doesn't change anything.