Irkhāʾ sirḥān evokes an extended stride like a wolf’s; sirḥān means a wolf. The legs reach forward in long, continuous movement.
Taqrīb tatful describes rapid movement with steps closer together; tatful is the young of a fox. These are not synonyms for one gait: the first stresses length and openness of stride, the second short, quick stepping.
The horse can vary its movement as conditions change. That versatility is central to the compliment.