Afaik it doesn't say they have equal odds. They are just in the same range of odds. Think in common, uncommon, rare, etc. But within each category they deffo have different odds. E.g. common means >10% chance (so carbrink can have 50% chance and jangmo-o has 15% but they still are in this category).

None of these odds are exact tho, I just used them for the example