Must a creature with less than 30 feet of movement dash when effected by Symbol’s Fear effect?

The effect states:

Fear: Each target must make a Wisdom saving throw and becomes Frightened for 1 minute on a failed save. While Frightened, the target drops whatever it is holding and must move at least 30 feet away from the glyph on each of its turns, if able.

The "if able" is where I’m getting hung up. Yes, the creature is able to move 30 feet by dashing, however I’m not sure if that is intended, as it would severely limit certain PCs. If a creature only has 25 feet of movement, such as a gnome or halfling, are they forced to use there dash every turn to make that 30 feet minimum?
This was ruled in my game as no, since it meant 3 members of the party were still functional while the fourth would have been completely useless with having to dash every turn.