This Dragonite inclusion is likely because, as the game's first-ever pseudo-Legendary, Dragonite spawns were considered some of the most exciting encounters that could be had in the pre-Shiny days of the game due to intense rarity
Because of this, Wizards powered down mana rocks once again, with most cycles today being three mana (Banners, Keyrunes, Cluestones) or being two mana, coming into play tapped, and having an additional downside (like Corrupted Grafstone or Sphere of the Suns)
The condition
So if you want to open playtest cards, you'll need the convention version of Mystery Boosters
You can get the most value from the discover mechanic by casting the card without paying its mana cost
This card reminds me more of Ignoble Hierarch than traditional mana accelerants like Sylvan Caryatid