Nah, this is just a common conception error that made by non-Japanese. Ninjas are not "Ninja Warriors" as we commonly recognized in pop culture. In the Japanese history about 200 to 300 years ago, they are just bunch of people specialized in sabotage, espionage, assassination, and scouting. It is like modern special agents of ancient time. The so called ninjutsu has nothing to do the wit these mudras, it is simply a teaching of "how to" sabotage, espionage, assassination, and scouting.
These people are just normal farmers that taking mercenary on hire. Some higher rank Ninjas may be trained with combat skill, but most of them just trained with a technique similar to mode parkour. It does make sense for Ninja to have this trait in game simply it is a combination of Ninja + Rogue where parkour should be the basic requirement.
Also, dragoon do exist in realize, and often just bunch of calvary with heavy lance and armor. I do not expect them can even jump
