Maybe they decided to use the trademarks on the names in the article? Sounds like a catch22 if you ask me. Put the trademark on the word and they serve you up a DCMA. Don't put it on and then you rise the ire of GoPro since you didn't use the mark on the trademarked names of their products.
Trademarks aren't copyrights, and trademark law is separate from copyright law right up to them being authorized by different sections of the US constitution. The DMCA is a copyright law and has no bearing on trademark issues, and there is no analog in trademark law for the DMCA takedown/safe harbor procedure beyond traditional C&D letters. To properly analyze who has what rights here, you need to completely ignore everything related to the DMCA, and then you come to the conclusion that a product review that properly identifies who made the product is of course free to use the trademarked name of the product to discuss it. (And little TM and (R) symbols have nothing to do with it.)
