A type specimen is what a species is based on. The
type specimen of Montipora undata looks nothing like what we in the hobby call M. undata. Anybody can call any coral M. undata, but at the end of the day, only corals conforming to the morphology or genetics of said species's type specimen are Montipora undata.
Corals of the World is rife with misidentifications, and many of Veron's species concepts were wrong, so I would not fully trust CotW as a species-level ID guide. That being said, most of the photos in
CotW's Montipora undata page look on par for M. undata, and are more similar to M. confusa than what the hobby calls M. undata.
Photo 11, which the hobby's concept of M. undata is likely based on, is a misidentification.