The reason for that is simple: the hexproof from the Swiftfoot Boots is more flexible than the shroud from the Lightning Greaves
While not as effective, Lotus Petal is another good source of quick mana if needed
This card generates some of its own dinosaurs to buff if you suspend it, which can be worth the wait since the tokens have flying and are relatively strong once you get this Boros creature on the field
The card was an uncommon, so it wanted to be simple
More specifically, you'll need to attend a prerelease event for the set at a Disney Park, and these promo cards will be handed out to those who are in the queue waiting to buy their Wilds Unknown products, according to those who have attended previous events.
The Mauler is a 4/4 with trample, while the Valesk is a 4/2