On PHB p. 50, the Totem Warrior Barbarian's Wolf totem for the 6th-level Aspect of the Beast feature grants the following benefit:
You gain the hunting sensibilities of a wolf. You can track other creatures while traveling at a fast pace, and you can move stealthily while traveling at a normal pace (see chapter 8 for rules on travel pace).
On PHB p. 182, the Travel Pace chart says that you can normally only move stealthily at a slow pace, but there is no mention of a restriction on travel pace for tracking. The stealth benefit for the Wolf aspect is useful at least. A fast pace causes a -5 to passive Wisdom (Perception) scores only. The Track activity under "Other Activities" on PHB p. 183 states:
A character can follow the tracks of another creature, making a Wisdom (Survival) check when the DM calls for it.
Again, there is no mention of travel pace being a factor. A check of the DMG section on tracking, DMG p. 244, lists several modifications for checks to track, none of which mention travel pace. Even the "Chases" section (DMG p. 253-255) doesn't mention anything where this part of the Wolf aspect would come into play.
Does the tracking at fast speed portion of the Wolf Aspect of the Beast adjust a game mechanic?