The benefit of the feat Pebble Underfoot (which has as its only prerequisite the feat Improved Trip) says
When attempting to trip a creature at least two size categories larger than you, you gain a +4 bonus on opposed trip checks. If you fail to trip the creature, it cannot immediately attempt to trip you. (Dragon Compendium Volume 1 103)
However, the Player's Handbook on Trip says
You can try to trip an opponent as an unarmed melee attack. You can only trip an opponent who is one size category larger than you, the same size, or smaller. (158)
Is the benefit of the feat Pebble Underfoot tacitly but specifically allowing the creature that possesses the feat to trip foes that are two or more size categories larger than it, or must the creature find its own way to trip such foes to gain the benefit of the feat? If the latter, what are the ways to trip such oversized creatures so that the feat's benefit can be realized?
Note: While the Dragon Compendium Volume 1 has a really nice errata document (Caution: PDF, and, hey, look at that erratum on the feat Dead Eye!), this feat goes unmentioned. When originally presented, the feat's language was slightly different, but the benefit was essentially the same (Dragon #279 63) (Third Edition and 3.5 have the same size limits for trip.) The feat is mentioned as an appropriate if niche feat in several trip-build handbooks, but the limitation regarding the target's size goes unmentioned.