It depends on the route, although the Dreamliners would have less cargo capacity than 747/777 aircraft. Probably KLM has been having problems with cargo needs on this aircraft type and decided that it would be simpler to ban checked pets across the aircraft type rather than on a long list of specific routes and dates.

Perishable cargo from AMS would obviously include flowers and cheese.

BTW, is there a difference between sending the dog as checked luggage versus as cargo on the same flight? Some airlines do both and have somewhat different rules and procedures, although typically very large dogs can travel only as cargo.